diff --git a/core/src/cell.rs b/core/src/cell.rs
index 96214710a1..da180d2249 100644
--- a/core/src/cell.rs
+++ b/core/src/cell.rs
@@ -217,7 +217,7 @@ mod tests {
             capacity: 2,
             data: vec![],
             lock: H256::default(),
-            contract: None,
+            type_: None,
         };
 
         db.cells.insert(p1.clone(), Some(o.clone()));
diff --git a/core/src/error.rs b/core/src/error.rs
index c1e56af1a9..192fe039a3 100644
--- a/core/src/error.rs
+++ b/core/src/error.rs
@@ -18,11 +18,3 @@ impl From<CrypError> for Error {
         Error::InvalidSignature(e)
     }
 }
-
-#[derive(Debug, PartialEq, Eq)]
-pub enum TxError {
-    OutOfBound,
-    NotMatch,
-    EmptyGroup,
-    WrongFormat,
-}
diff --git a/core/src/transaction.rs b/core/src/transaction.rs
index ccaf942835..a643998caf 100644
--- a/core/src/transaction.rs
+++ b/core/src/transaction.rs
@@ -79,16 +79,17 @@ pub struct CellOutput {
     pub capacity: Capacity,
     pub data: Vec<u8>,
     pub lock: H256,
-    pub contract: Option<Script>,
+    #[serde(rename = "type")]
+    pub type_: Option<Script>,
 }
 
 impl CellOutput {
-    pub fn new(capacity: Capacity, data: Vec<u8>, lock: H256, contract: Option<Script>) -> Self {
+    pub fn new(capacity: Capacity, data: Vec<u8>, lock: H256, type_: Option<Script>) -> Self {
         CellOutput {
             capacity,
             data,
             lock,
-            contract,
+            type_,
         }
     }
 
@@ -110,7 +111,7 @@ impl CellOutput {
         mem::size_of::<Capacity>()
             + self.data.len()
             + H256::size_of()
-            + self.contract.as_ref().map_or(0, |s| s.bytes_len())
+            + self.type_.as_ref().map_or(0, |s| s.bytes_len())
     }
 }
 
diff --git a/protocol/src/builder.rs b/protocol/src/builder.rs
index 6d91b7f6ed..3260eb9b56 100644
--- a/protocol/src/builder.rs
+++ b/protocol/src/builder.rs
@@ -172,16 +172,13 @@ impl<'a> FbsCellOutput<'a> {
     ) -> WIPOffset<FbsCellOutput<'b>> {
         let data = FbsBytes::build(fbb, &cell_output.data);
         let lock = FbsBytes::build(fbb, &cell_output.lock.as_bytes());
-        let contract = cell_output
-            .contract
-            .as_ref()
-            .map(|s| FbsScript::build(fbb, s));
+        let type_ = cell_output.type_.as_ref().map(|s| FbsScript::build(fbb, s));
         let mut builder = CellOutputBuilder::new(fbb);
         builder.add_capacity(cell_output.capacity);
         builder.add_data(data);
         builder.add_lock(lock);
-        if let Some(s) = contract {
-            builder.add_contract(s);
+        if let Some(s) = type_ {
+            builder.add_type_(s);
         }
         builder.finish()
     }
diff --git a/protocol/src/convert.rs b/protocol/src/convert.rs
index 5c48fd0901..f5e790e6ba 100644
--- a/protocol/src/convert.rs
+++ b/protocol/src/convert.rs
@@ -154,7 +154,7 @@ impl<'a> From<ckb_protocol::CellOutput<'a>> for ckb_core::transaction::CellOutpu
             capacity: cell_output.capacity(),
             data: cell_output.data().and_then(|b| b.seq()).unwrap().to_vec(),
             lock: H256::from_slice(cell_output.lock().and_then(|b| b.seq()).unwrap()).unwrap(),
-            contract: cell_output.contract().map(Into::into),
+            type_: cell_output.type_().map(Into::into),
         }
     }
 }
diff --git a/protocol/src/protocol.fbs b/protocol/src/protocol.fbs
index c0cb272110..5bb4abd973 100644
--- a/protocol/src/protocol.fbs
+++ b/protocol/src/protocol.fbs
@@ -79,7 +79,7 @@ table CellOutput {
     capacity:       uint64;
     data:           Bytes;
     lock:           Bytes;
-    contract:       Script;
+    type:           Script;
 }
 
 table Script {
diff --git a/protocol/src/protocol_generated.rs b/protocol/src/protocol_generated.rs
index 06b5955265..0079784146 100644
--- a/protocol/src/protocol_generated.rs
+++ b/protocol/src/protocol_generated.rs
@@ -1376,7 +1376,7 @@ impl<'a> CellOutput<'a> {
         args: &'args CellOutputArgs<'args>) -> flatbuffers::WIPOffset<CellOutput<'bldr>> {
       let mut builder = CellOutputBuilder::new(_fbb);
       builder.add_capacity(args.capacity);
-      if let Some(x) = args.contract { builder.add_contract(x); }
+      if let Some(x) = args.type_ { builder.add_type_(x); }
       if let Some(x) = args.lock { builder.add_lock(x); }
       if let Some(x) = args.data { builder.add_data(x); }
       builder.finish()
@@ -1385,7 +1385,7 @@ impl<'a> CellOutput<'a> {
     pub const VT_CAPACITY: flatbuffers::VOffsetT = 4;
     pub const VT_DATA: flatbuffers::VOffsetT = 6;
     pub const VT_LOCK: flatbuffers::VOffsetT = 8;
-    pub const VT_CONTRACT: flatbuffers::VOffsetT = 10;
+    pub const VT_TYPE_: flatbuffers::VOffsetT = 10;
 
   #[inline]
   pub fn capacity(&self) -> u64 {
@@ -1400,8 +1400,8 @@ impl<'a> CellOutput<'a> {
     self._tab.get::<flatbuffers::ForwardsUOffset<Bytes<'a>>>(CellOutput::VT_LOCK, None)
   }
   #[inline]
-  pub fn contract(&self) -> Option<Script<'a>> {
-    self._tab.get::<flatbuffers::ForwardsUOffset<Script<'a>>>(CellOutput::VT_CONTRACT, None)
+  pub fn type_(&self) -> Option<Script<'a>> {
+    self._tab.get::<flatbuffers::ForwardsUOffset<Script<'a>>>(CellOutput::VT_TYPE_, None)
   }
 }
 
@@ -1409,7 +1409,7 @@ pub struct CellOutputArgs<'a> {
     pub capacity: u64,
     pub data: Option<flatbuffers::WIPOffset<Bytes<'a >>>,
     pub lock: Option<flatbuffers::WIPOffset<Bytes<'a >>>,
-    pub contract: Option<flatbuffers::WIPOffset<Script<'a >>>,
+    pub type_: Option<flatbuffers::WIPOffset<Script<'a >>>,
 }
 impl<'a> Default for CellOutputArgs<'a> {
     #[inline]
@@ -1418,7 +1418,7 @@ impl<'a> Default for CellOutputArgs<'a> {
             capacity: 0,
             data: None,
             lock: None,
-            contract: None,
+            type_: None,
         }
     }
 }
@@ -1440,8 +1440,8 @@ impl<'a: 'b, 'b> CellOutputBuilder<'a, 'b> {
     self.fbb_.push_slot_always::<flatbuffers::WIPOffset<Bytes>>(CellOutput::VT_LOCK, lock);
   }
   #[inline]
-  pub fn add_contract(&mut self, contract: flatbuffers::WIPOffset<Script<'b >>) {
-    self.fbb_.push_slot_always::<flatbuffers::WIPOffset<Script>>(CellOutput::VT_CONTRACT, contract);
+  pub fn add_type_(&mut self, type_: flatbuffers::WIPOffset<Script<'b >>) {
+    self.fbb_.push_slot_always::<flatbuffers::WIPOffset<Script>>(CellOutput::VT_TYPE_, type_);
   }
   #[inline]
   pub fn new(_fbb: &'b mut flatbuffers::FlatBufferBuilder<'a>) -> CellOutputBuilder<'a, 'b> {
diff --git a/rpc/doc.md b/rpc/doc.md
index 4718d63782..248ca7e3cf 100644
--- a/rpc/doc.md
+++ b/rpc/doc.md
@@ -58,7 +58,7 @@ curl -d '{"id": 2, "jsonrpc": "2.0", "method":"get_block","params": ["0x7643567c
                     "outputs": [
                         {
                             "capacity": 50000,
-                            "contract": null,
+                            "type_": null,
                             "data": [],
                             "lock": "0x321c1ca2887fb8eddaaa7e917399f71e63e03a1c83ff75ed12099a01115ea2ff"
                         }
@@ -111,7 +111,7 @@ curl -d '{"id": 2, "jsonrpc": "2.0", "method":"get_transaction","params": ["0xbd
             "outputs": [
                 {
                     "capacity": 50000,
-                    "contract": null,
+                    "type_": null,
                     "data": [],
                     "lock": "0x321c1ca2887fb8eddaaa7e917399f71e63e03a1c83ff75ed12099a01115ea2ff"
                 }
@@ -267,7 +267,7 @@ curl -d '{"id": 2, "jsonrpc": "2.0", "method":"get_current_cell","params": [{"ha
     "result": {
         "cell": {
             "capacity": 50000,
-            "contract": null,
+            "type_": null,
             "data": [],
             "lock": "0x321c1ca2887fb8eddaaa7e917399f71e63e03a1c83ff75ed12099a01115ea2ff"
         },
diff --git a/script/src/syscalls/fetch_script_hash.rs b/script/src/syscalls/fetch_script_hash.rs
index dc86bc8d9e..bfab1ab9eb 100644
--- a/script/src/syscalls/fetch_script_hash.rs
+++ b/script/src/syscalls/fetch_script_hash.rs
@@ -37,9 +37,9 @@ impl<'a> FetchScriptHash<'a> {
             (Source::INPUT, Category::CONTRACT) => {
                 self.input_cells.get(index).and_then(|input_cell| {
                     input_cell
-                        .contract
+                        .type_
                         .as_ref()
-                        .map(|contract| contract.type_hash())
+                        .map(|type_| type_.type_hash())
                 })
             }
             (Source::OUTPUT, Category::LOCK) => {
@@ -47,9 +47,9 @@ impl<'a> FetchScriptHash<'a> {
             }
             (Source::OUTPUT, Category::CONTRACT) => self.outputs.get(index).and_then(|output| {
                 output
-                    .contract
+                    .type_
                     .as_ref()
-                    .map(|contract| contract.type_hash())
+                    .map(|type_| type_.type_hash())
             }),
         }
     }
diff --git a/script/src/syscalls/load_cell_by_field.rs b/script/src/syscalls/load_cell_by_field.rs
index 0aa6f823cb..609462b133 100644
--- a/script/src/syscalls/load_cell_by_field.rs
+++ b/script/src/syscalls/load_cell_by_field.rs
@@ -80,10 +80,10 @@ impl<'a, R: Register, M: Memory> Syscalls<R, M> for LoadCellByField<'a> {
                 store_data(machine, &cell.lock.as_bytes())?;
                 SUCCESS
             }
-            CellField::Contract => match cell.contract {
-                Some(ref contract) => {
+            CellField::Type => match cell.type_ {
+                Some(ref type_) => {
                     let mut builder = FlatBufferBuilder::new();
-                    let offset = FbsScript::build(&mut builder, &contract);
+                    let offset = FbsScript::build(&mut builder, &type_);
                     builder.finish(offset, None);
                     let data = builder.finished_data();
                     store_data(machine, data)?;
@@ -91,9 +91,9 @@ impl<'a, R: Register, M: Memory> Syscalls<R, M> for LoadCellByField<'a> {
                 }
                 None => ITEM_MISSING,
             },
-            CellField::ContractHash => match cell.contract {
-                Some(ref contract) => {
-                    store_data(machine, &contract.type_hash().as_bytes())?;
+            CellField::TypeHash => match cell.type_ {
+                Some(ref type_) => {
+                    store_data(machine, &type_.type_hash().as_bytes())?;
                     SUCCESS
                 }
                 None => ITEM_MISSING,
diff --git a/script/src/syscalls/mod.rs b/script/src/syscalls/mod.rs
index bbf1f77b55..03f789f3a1 100644
--- a/script/src/syscalls/mod.rs
+++ b/script/src/syscalls/mod.rs
@@ -30,8 +30,8 @@ enum CellField {
     Data = 1,
     DataHash = 2,
     LockHash = 3,
-    Contract = 4,
-    ContractHash = 5,
+    Type = 4,
+    TypeHash = 5,
 }
 
 impl CellField {
@@ -41,8 +41,8 @@ impl CellField {
             1 => Ok(CellField::Data),
             2 => Ok(CellField::DataHash),
             3 => Ok(CellField::LockHash),
-            4 => Ok(CellField::Contract),
-            5 => Ok(CellField::ContractHash),
+            4 => Ok(CellField::Type),
+            5 => Ok(CellField::TypeHash),
             _ => Err(Error::ParseError),
         }
     }
@@ -594,7 +594,7 @@ mod tests {
         machine.registers_mut()[A2] = 0; // offset
         machine.registers_mut()[A3] = 0; //index
         machine.registers_mut()[A4] = Source::Output as u64; //source: 2 output
-        machine.registers_mut()[A5] = CellField::Contract as u64; //field: 4 contract
+        machine.registers_mut()[A5] = CellField::Type as u64; //field: 4 type
         machine.registers_mut()[A7] = LOAD_CELL_BY_FIELD_SYSCALL_NUMBER; // syscall number
 
         let output_cell = CellOutput::new(100, vec![], H256::default(), None);
diff --git a/script/src/verify.rs b/script/src/verify.rs
index ff9fbb9a21..e56aed94de 100644
--- a/script/src/verify.rs
+++ b/script/src/verify.rs
@@ -175,9 +175,9 @@ impl<'a> TransactionScriptsVerifier<'a> {
             })?;
         }
         for (i, output) in self.outputs.iter().enumerate() {
-            if let Some(ref contract) = output.contract {
+            if let Some(ref type_) = output.type_ {
                 let prefix = format!("Transaction {}, output {}", self.hash, i);
-                self.verify_script(contract, &prefix, output, None).map_err(|e| {
+                self.verify_script(type_, &prefix, output, None).map_err(|e| {
                     info!(target: "script", "Error validating output {} of transaction {}: {:?}", i, self.hash, e);
                     e
                 })?;