diff --git a/overlays/deploy/prometheusrule.yaml b/overlays/deploy/prometheusrule.yaml
index 56655cc9..de87870b 100644
--- a/overlays/deploy/prometheusrule.yaml
+++ b/overlays/deploy/prometheusrule.yaml
@@ -11,5 +11,5 @@ spec:
   groups:
     - name: acm_managed_cluster_worker_cores.rules
       rules:
-        - expr: sum by (hub_cluster_id, managed_cluster_id) (acm_managed_cluster_worker_cores)
-          record: 'acm_managed_cluster_worker_cores:sum'
+        - expr: max by (hub_cluster_id, managed_cluster_id) (acm_managed_cluster_worker_cores)
+          record: 'acm_managed_cluster_worker_cores:max'
diff --git a/overlays/test/http/prometheusrule.yaml b/overlays/test/http/prometheusrule.yaml
index 6cdf7451..e5439546 100644
--- a/overlays/test/http/prometheusrule.yaml
+++ b/overlays/test/http/prometheusrule.yaml
@@ -12,5 +12,5 @@ spec:
   groups:
     - name: acm_managed_cluster_worker_cores.rules
       rules:
-        - expr: sum by (hub_cluster_id, managed_cluster_id) (acm_managed_cluster_worker_cores)
-          record: 'acm_managed_cluster_worker_cores:sum'
+        - expr: max by (hub_cluster_id, managed_cluster_id) (acm_managed_cluster_worker_cores)
+          record: 'acm_managed_cluster_worker_cores:max'
diff --git a/test/functional/managedcluster_test.go b/test/functional/managedcluster_test.go
index cac75ecd..debbbba2 100644
--- a/test/functional/managedcluster_test.go
+++ b/test/functional/managedcluster_test.go
@@ -547,7 +547,7 @@ var _ = Describe("ManagedCluster Metrics", func() {
 	})
 
 	Context("acm_managed_cluster_worker_cores", func() {
-		ruleExpr := "sum(acm_managed_cluster_worker_cores)+by+(hub_cluster_id,managed_cluster_id)"
+		ruleExpr := "max(acm_managed_cluster_worker_cores)+by+(hub_cluster_id,managed_cluster_id)"
 
 		AfterEach(func() {
 			By("Query metrics by count(acm_managed_cluster_worker_cores) by (hub_cluster_id)", func() {
@@ -582,7 +582,7 @@ var _ = Describe("ManagedCluster Metrics", func() {
 
 		It("should get metric", func() {
 			assertGetMetrics("acm_managed_cluster_worker_cores", clusterWorkerCoresResponse)
-			assertRecordingRule("acm_managed_cluster_worker_cores:sum", ruleExpr)
+			assertRecordingRule("acm_managed_cluster_worker_cores:max", ruleExpr)
 		})
 
 		It("should reflect the change on the managed cluster", func() {
@@ -595,7 +595,7 @@ var _ = Describe("ManagedCluster Metrics", func() {
 			})
 
 			assertGetMetrics("acm_managed_cluster_worker_cores", clusterWorkerCoresUpdatedResponse)
-			assertRecordingRule("acm_managed_cluster_worker_cores:sum", ruleExpr)
+			assertRecordingRule("acm_managed_cluster_worker_cores:max", ruleExpr)
 		})
 	})
 })