diff --git a/src/api.rs b/src/api.rs
index f5c418e..78613f1 100644
--- a/src/api.rs
+++ b/src/api.rs
@@ -13,7 +13,7 @@ pub async fn register_rpc(params: Params, db: &RocksDB) -> Result<Value, Error>
     info!("Register cota cells request: {:?}", params);
     let registries: Vec<Value> = Params::parse(params)?;
     let lock_hashes = parse_request_param::<32>(registries).map_err(|err| err.into())?;
-    let (root_hash, registry_entry) = generate_registry_smt(db, lock_hashes)
+    let (root_hash, registry_entry, output_account_num) = generate_registry_smt(db, lock_hashes)
         .await
         .map_err(|err| err.into())?;
     let block_number = get_syncer_tip_block_number().map_err(|err| err.into())?;
@@ -23,6 +23,10 @@ pub async fn register_rpc(params: Params, db: &RocksDB) -> Result<Value, Error>
         "registry_smt_entry".to_string(),
         Value::String(registry_entry),
     );
+    response.insert(
+        "output_account_num".to_string(),
+        Value::Number(Number::from(output_account_num)),
+    );
     response.insert(
         "block_number".to_string(),
         Value::Number(Number::from(block_number)),
@@ -51,7 +55,7 @@ pub async fn check_registered_rpc(params: Params) -> Result<Value, Error> {
 pub async fn update_registered_ccid_rpc(db: &RocksDB) -> Result<Value, Error> {
     info!("Update registered ccid request");
     let lock_hashes = get_50_registered_lock_hashes().map_err(|err| err.into())?;
-    let (root_hash, registry_entry) = generate_registry_smt(db, lock_hashes)
+    let (root_hash, registry_entry, output_account_num) = generate_registry_smt(db, lock_hashes)
         .await
         .map_err(|err| err.into())?;
     let block_number = get_syncer_tip_block_number().map_err(|err| err.into())?;
@@ -61,6 +65,10 @@ pub async fn update_registered_ccid_rpc(db: &RocksDB) -> Result<Value, Error> {
         "registry_smt_entry".to_string(),
         Value::String(registry_entry),
     );
+    response.insert(
+        "output_account_num".to_string(),
+        Value::Number(Number::from(output_account_num)),
+    );
     response.insert(
         "block_number".to_string(),
         Value::Number(Number::from(block_number)),
diff --git a/src/smt/entry.rs b/src/smt/entry.rs
index 25d0cdb..765278d 100644
--- a/src/smt/entry.rs
+++ b/src/smt/entry.rs
@@ -23,7 +23,7 @@ lazy_static! {
 pub async fn generate_registry_smt(
     db: &RocksDB,
     lock_hashes: Vec<[u8; 32]>,
-) -> Result<(String, String), Error> {
+) -> Result<(String, String, u64), Error> {
     let update_leaves_count = lock_hashes.len();
     let registry_state = check_lock_hashes_registered(lock_hashes.clone())?.0;
     if registry_state == RegistryState::WithCCID {
@@ -36,6 +36,7 @@ pub async fn generate_registry_smt(
         smt_root,
         account_num,
     } = get_registry_info().await?;
+    let output_account_num = account_num + lock_hashes.len() as u64;
     for (index, lock_hash) in lock_hashes.into_iter().enumerate() {
         let key: H256 = H256::from(lock_hash);
         registry_value[0..8].copy_from_slice(&(account_num + index as u64).to_be_bytes());
@@ -103,7 +104,7 @@ pub async fn generate_registry_smt(
 
     let registry_entry = hex::encode(registry_entries.as_slice());
 
-    Ok((root_hash, registry_entry))
+    Ok((root_hash, registry_entry, output_account_num))
 }
 
 fn with_lock<F>(mut operator: F) -> Result<(), Error>