diff --git a/.github/workflows/composite_action/hw/action.yml b/.github/workflows/composite_action/hw/action.yml
index dd7e68a1..efe3ed35 100644
--- a/.github/workflows/composite_action/hw/action.yml
+++ b/.github/workflows/composite_action/hw/action.yml
@@ -11,7 +11,7 @@ inputs:
   os:
     description: 'Occlum docker image base OS'
     required: false
-    default: 'ubuntu18.04'
+    default: 'ubuntu20.04'
 
 runs:
   using: "composite"
diff --git a/.github/workflows/composite_action/sim/action.yml b/.github/workflows/composite_action/sim/action.yml
index 7576f2e5..dc6076c3 100644
--- a/.github/workflows/composite_action/sim/action.yml
+++ b/.github/workflows/composite_action/sim/action.yml
@@ -11,7 +11,7 @@ inputs:
   os:
     description: 'Occlum docker image base OS'
     required: false
-    default: 'ubuntu18.04'
+    default: 'ubuntu20.04'
 
 runs:
   using: "composite"