diff --git a/.github/workflows/check.yml b/.github/workflows/check.yml
index 248b177..9387ad4 100644
--- a/.github/workflows/check.yml
+++ b/.github/workflows/check.yml
@@ -47,6 +47,9 @@ jobs:
           moonrun --version
 
       - name: moon test
+        env:
+          # just for testing env var
+          MOON_TEST: "yes"
         run: |
           moon test --target all --serial --release
           moon test --target all --serial
diff --git a/fs/internal/ffi/fs_wasm.mbt b/fs/internal/ffi/fs_wasm.mbt
index bb035f5..4acb26e 100644
--- a/fs/internal/ffi/fs_wasm.mbt
+++ b/fs/internal/ffi/fs_wasm.mbt
@@ -13,9 +13,10 @@
 // limitations under the License.
 
 typealias XExternString = @ffi.XExternString
+
 typealias XExternByteArray = @ffi.XExternByteArray
-typealias XExternStringArray = @ffi.XExternStringArray
 
+typealias XExternStringArray = @ffi.XExternStringArray
 
 pub fn read_file_to_string(path : String) -> String {
   let path = @ffi.string_to_extern(path)
diff --git a/sys/internal/ffi/ffi.mbti b/sys/internal/ffi/ffi.mbti
new file mode 100644
index 0000000..7263e3b
--- /dev/null
+++ b/sys/internal/ffi/ffi.mbti
@@ -0,0 +1,13 @@
+package moonbitlang/x/sys/internal/ffi
+
+// Values
+fn get_cli_args() -> Array[String]
+
+fn get_env_var(String) -> String
+
+// Types and methods
+
+// Type aliases
+
+// Traits
+
diff --git a/sys/internal/ffi/moon.pkg.json b/sys/internal/ffi/moon.pkg.json
new file mode 100644
index 0000000..70abf47
--- /dev/null
+++ b/sys/internal/ffi/moon.pkg.json
@@ -0,0 +1,10 @@
+{
+    "import": [
+        "moonbitlang/x/internal/ffi"
+    ],
+    "targets": {
+        "sys_wasm.mbt": ["wasm", "wasm-gc"],
+        "sys_js.mbt": ["js"],
+        "sys_native.mbt": ["native"]
+    }
+}
\ No newline at end of file
diff --git a/sys/internal/ffi/sys_js.mbt b/sys/internal/ffi/sys_js.mbt
new file mode 100644
index 0000000..5f29be3
--- /dev/null
+++ b/sys/internal/ffi/sys_js.mbt
@@ -0,0 +1,31 @@
+// Copyright 2024 International Digital Economy Academy
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+pub fn get_cli_args() -> Array[String] {
+  get_cli_args_internal()
+}
+
+extern "js" fn get_cli_args_internal() -> Array[String] =
+  #| function() {
+  #|  return process.argv.slice(2);
+  #| }
+
+pub fn get_env_var(s : String) -> String {
+  get_env_var_internal(s)
+}
+
+extern "js" fn get_env_var_internal(s : String) -> String =
+  #| function(s) {
+  #|  return process.env[s];
+  #| }
diff --git a/sys/internal/ffi/sys_native.mbt b/sys/internal/ffi/sys_native.mbt
new file mode 100644
index 0000000..d9fe2d6
--- /dev/null
+++ b/sys/internal/ffi/sys_native.mbt
@@ -0,0 +1,23 @@
+// Copyright 2024 International Digital Economy Academy
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+pub fn get_cli_args() -> Array[String] {
+  // not implement yet
+  panic()
+}
+
+pub fn get_env_var(_s : String) -> String {
+  // not implement yet
+  panic()
+}
diff --git a/sys/internal/ffi/sys_wasm.mbt b/sys/internal/ffi/sys_wasm.mbt
new file mode 100644
index 0000000..0fe76b8
--- /dev/null
+++ b/sys/internal/ffi/sys_wasm.mbt
@@ -0,0 +1,32 @@
+// Copyright 2024 International Digital Economy Academy
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+typealias XExternString = @ffi.XExternString
+
+typealias XExternStringArray = @ffi.XExternStringArray
+
+pub fn get_cli_args() -> Array[String] {
+  let args = get_cli_args_ffi()
+  @ffi.string_array_from_extern(args)
+}
+
+fn get_cli_args_ffi() -> XExternStringArray = "__moonbit_fs_unstable" "args_get"
+
+pub fn get_env_var(s : String) -> String {
+  let s = @ffi.string_to_extern(s)
+  let res = get_env_var_ffi(s)
+  @ffi.string_from_extern(res)
+}
+
+fn get_env_var_ffi(s : XExternString) -> XExternString = "__moonbit_fs_unstable" "env_get_var"
diff --git a/sys/moon.pkg.json b/sys/moon.pkg.json
new file mode 100644
index 0000000..6fa5364
--- /dev/null
+++ b/sys/moon.pkg.json
@@ -0,0 +1,8 @@
+{
+    "import": [
+        "moonbitlang/x/sys/internal/ffi"
+    ],
+    "targets": {
+        "sys_test.mbt": ["not", "native"]
+    }
+}
diff --git a/sys/sys.mbt b/sys/sys.mbt
new file mode 100644
index 0000000..d0e97f9
--- /dev/null
+++ b/sys/sys.mbt
@@ -0,0 +1,21 @@
+// Copyright 2024 International Digital Economy Academy
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+pub fn get_cli_args() -> Array[String] {
+  @ffi.get_cli_args()
+}
+
+pub fn get_env_var(s : String) -> String {
+  @ffi.get_env_var(s)
+}
diff --git a/sys/sys.mbti b/sys/sys.mbti
new file mode 100644
index 0000000..b4e817d
--- /dev/null
+++ b/sys/sys.mbti
@@ -0,0 +1,13 @@
+package moonbitlang/x/sys
+
+// Values
+fn get_cli_args() -> Array[String]
+
+fn get_env_var(String) -> String
+
+// Types and methods
+
+// Type aliases
+
+// Traits
+
diff --git a/sys/sys_test.mbt b/sys/sys_test.mbt
new file mode 100644
index 0000000..7ebf66c
--- /dev/null
+++ b/sys/sys_test.mbt
@@ -0,0 +1,18 @@
+// Copyright 2024 International Digital Economy Academy
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+test "get_env_var" {
+  let res = @sys.get_env_var("MOON_TEST")
+  inspect!(res, content="yes")
+}