diff --git a/Cargo.toml b/Cargo.toml
index 388e1cb..ad065a1 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -13,7 +13,8 @@ members = [
     "examples/call-neovm",
     "examples/invoke-native-test",
     "examples/notify-test",
-    "examples/call_native"
+    "examples/call_native",
+    "examples/oracle"
 ]
 
 [profile.release]
diff --git a/examples/oracle/Cargo.toml b/examples/oracle/Cargo.toml
new file mode 100644
index 0000000..4bbdeb4
--- /dev/null
+++ b/examples/oracle/Cargo.toml
@@ -0,0 +1,19 @@
+[package]
+name = "oracle"
+version = "0.1.0"
+authors = ["qiluge <wangcheng@onchain.com>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+
+ontio-std = {git = "https://github.com/ontio/ontology-wasm-cdt-rust"}
+
+
+[lib]
+crate-type = ["cdylib", "rlib"] #Compile as a dynamic link library
+
+
+[features]
+mock = ["ontio-std/mock"]
\ No newline at end of file
diff --git a/examples/oracle/src/lib.rs b/examples/oracle/src/lib.rs
new file mode 100644
index 0000000..1b96530
--- /dev/null
+++ b/examples/oracle/src/lib.rs
@@ -0,0 +1,59 @@
+#![cfg_attr(not(feature = "mock"), no_std)]
+#![feature(proc_macro_hygiene)]
+extern crate ontio_std as ostd;
+
+use ostd::abi::{Sink, Source};
+use ostd::prelude::*;
+use ostd::runtime::{check_witness, input, ret};
+
+use method::*;
+use storage::*;
+
+pub mod method;
+pub mod storage;
+
+#[no_mangle]
+pub fn invoke() {
+    let input = input();
+    let mut source = Source::new(&input);
+    let action: &[u8] = source.read().unwrap();
+    let mut sink = Sink::new(12);
+    match action {
+        b"init" => {
+            let admin = source.read().unwrap();
+            sink.write(initialize(admin));
+        }
+        b"isPriceOracle" => {
+            sink.write(true);
+        }
+        b"putUnderlyingPrice" => {
+            let (key_list, price_list) = source.read().unwrap();
+            sink.write(put_underlying_price(key_list, price_list));
+        }
+        b"getUnderlyingPrice" => {
+            let key = source.read().unwrap();
+            sink.write(get_price(key));
+        }
+        b"setDecimal" => {
+            let decimal = source.read().unwrap();
+            assert!(check_witness(&get_admin()), "check witness failed");
+            sink.write(put_decimal(decimal));
+        }
+        b"getDecimal" => {
+            sink.write(get_decimal());
+        }
+        _ => {
+            let method = str::from_utf8(action).ok().unwrap();
+            panic!("not support method:{}", method)
+        }
+    }
+    ret(sink.bytes());
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn it_works() {
+        assert_eq!(2 + 2, 4);
+    }
+}
diff --git a/examples/oracle/src/method.rs b/examples/oracle/src/method.rs
new file mode 100644
index 0000000..de4c7d1
--- /dev/null
+++ b/examples/oracle/src/method.rs
@@ -0,0 +1,30 @@
+use ostd::abi::EventBuilder;
+use ostd::prelude::*;
+use ostd::runtime::check_witness;
+use ostd::types::U128;
+
+use crate::storage::*;
+
+/**
+ * @notice Initialize the money market
+ * @param admin The address of the Oracle
+ */
+pub fn initialize(admin: &Address) {
+    assert!(check_witness(&admin), "check witness failed");
+    assert!(!is_init(), "already init");
+    put_admin(admin);
+    init();
+}
+
+pub fn put_underlying_price(key_list: Vec<&str>, price_list: Vec<U128>) {
+    assert!(check_witness(&get_admin()), "check witness failed");
+    assert_eq!(key_list.len(), price_list.len(), "invalid param");
+    let mut event_builder = EventBuilder::new();
+    event_builder = event_builder.string("PutUnderlyingPrice");
+    for (key, price) in key_list.into_iter().zip(price_list.into_iter()) {
+        put_price(key, price);
+        event_builder = event_builder.string(key);
+        event_builder = event_builder.number(price);
+    }
+    event_builder.notify()
+}
diff --git a/examples/oracle/src/storage.rs b/examples/oracle/src/storage.rs
new file mode 100644
index 0000000..ead0b8e
--- /dev/null
+++ b/examples/oracle/src/storage.rs
@@ -0,0 +1,52 @@
+use ostd::database;
+use ostd::prelude::*;
+use ostd::types::U128;
+
+/**
+ * @notice Administrator for this contract
+ */
+const ADMIN_KEY: &str = "admin";
+
+pub fn put_admin(admin: &Address) {
+    database::put(ADMIN_KEY, admin);
+}
+
+pub fn get_admin() -> Address {
+    database::get(ADMIN_KEY).unwrap()
+}
+
+const INIT: &str = "init";
+
+pub fn init() {
+    database::put(INIT, true);
+}
+
+pub fn is_init() -> bool {
+    database::get(INIT).unwrap_or(false)
+}
+
+/**
+ * @notice Price data for this contract
+ */
+const PRICE: &str = "price";
+
+pub fn put_price(key: &str, price: U128) {
+    database::put(PRICE.to_string() + key, price);
+}
+
+pub fn get_price(key: &str) -> U128 {
+    database::get(PRICE.to_string() + key).unwrap()
+}
+
+/**
+ * @notice Decimal for this contract
+ */
+const DECIMAL: &str = "decimal";
+
+pub fn put_decimal(decimal: u8) {
+    database::put(DECIMAL, decimal);
+}
+
+pub fn get_decimal() -> u8 {
+    database::get(DECIMAL).unwrap()
+}
diff --git a/examples/oracle/tests/tests.rs b/examples/oracle/tests/tests.rs
new file mode 100644
index 0000000..f328724
--- /dev/null
+++ b/examples/oracle/tests/tests.rs
@@ -0,0 +1,43 @@
+extern crate ontio_std as ostd;
+extern crate oracle;
+
+use ostd::types::U128;
+use ostd::{mock::build_runtime, prelude::*};
+
+use oracle::method;
+use oracle::storage;
+
+#[test]
+fn test_oracle() {
+    let runtime = &build_runtime();
+    let admin = Address::repeat_byte(1);
+    runtime.witness(&[admin.clone()]);
+    method::initialize(&admin);
+    storage::put_decimal(9);
+    assert_eq!(9, storage::get_decimal());
+    method::put_underlying_price(vec!["ONT", "BTC", "ETH", "DAI"], vec![100, 10000, 400, 1]);
+    assert_eq!(100, storage::get_price("ONT"));
+    assert_eq!(10000, storage::get_price("BTC"));
+    assert_eq!(400, storage::get_price("ETH"));
+    assert_eq!(1, storage::get_price("DAI"));
+}
+
+#[test]
+#[should_panic]
+fn test_init_twice() {
+    let runtime = &build_runtime();
+    let admin = Address::repeat_byte(1);
+    runtime.witness(&[admin.clone()]);
+    method::initialize(&admin);
+    method::initialize(&admin);
+}
+
+#[test]
+fn test_set_decimal_twice() {
+    let runtime = &build_runtime();
+    let admin = Address::repeat_byte(1);
+    runtime.witness(&[admin.clone()]);
+    method::initialize(&admin);
+    storage::put_decimal(9);
+    storage::put_decimal(7);
+}
diff --git a/ontio-std/src/abi/event_builder.rs b/ontio-std/src/abi/event_builder.rs
index d61400b..a602422 100644
--- a/ontio-std/src/abi/event_builder.rs
+++ b/ontio-std/src/abi/event_builder.rs
@@ -171,7 +171,7 @@ impl VmValueBuilderCommon {
 // compile-fails
 
 /// ```compile_fail
-/// #[deny(unused_must_use)]
+/// #![deny(unused_must_use)]
 /// {
 ///     EventBuilder::new().bool(true);
 /// }