diff --git a/apiserver/pkg/manager/resource_manager.go b/apiserver/pkg/manager/resource_manager.go
index 44bf401082..7810c046cd 100644
--- a/apiserver/pkg/manager/resource_manager.go
+++ b/apiserver/pkg/manager/resource_manager.go
@@ -109,6 +109,10 @@ func (r *ResourceManager) GetCluster(ctx context.Context, clusterName string, na
 		return nil, util.NewInvalidInputError("clusterName is empty, failed to get the cluster.")
 	}
 
+	if len(namespace) == 0 {
+		namespace = DefaultNamespace
+	}
+
 	client := r.getRayClusterClient(namespace)
 	return getClusterByName(ctx, client, clusterName)
 }
@@ -133,6 +137,10 @@ func (r *ResourceManager) DeleteCluster(ctx context.Context, clusterName string,
 		return util.NewInvalidInputError("clusterName is empty, failed to delete the cluster.")
 	}
 
+	if len(namespace) == 0 {
+		namespace = DefaultNamespace
+	}
+
 	client := r.getRayClusterClient(namespace)
 	cluster, err := getClusterByName(ctx, client, clusterName)
 	if err != nil {
diff --git a/apiserver/pkg/server/cluster_server.go b/apiserver/pkg/server/cluster_server.go
index 88ce62bd56..682d582e20 100644
--- a/apiserver/pkg/server/cluster_server.go
+++ b/apiserver/pkg/server/cluster_server.go
@@ -80,10 +80,6 @@ func ValidateCreateClusterRequest(request *api.CreateClusterRequest) error {
 		return util.NewInvalidInputError("User who create the cluster is empty. Please specify a valid value.")
 	}
 
-	if request.Cluster.Namespace == "" {
-		return util.NewInvalidInputError("Namespace is empty. Please specify a valid value.")
-	}
-
 	if len(request.Cluster.ClusterSpec.HeadGroupSpec.ComputeTemplate) == 0 {
 		return util.NewInvalidInputError("HeadGroupSpec compute template is empty. Please specify a valid value.")
 	}