diff --git a/pkg/utils/helm/helm_helper.go b/pkg/utils/helm/helm_helper.go
index d47899c09..d871426fd 100644
--- a/pkg/utils/helm/helm_helper.go
+++ b/pkg/utils/helm/helm_helper.go
@@ -140,20 +140,16 @@ func (h *Helper) UpgradeChart(ch *chart.Chart, releaseName, namespace string, va
 				r.Info.Status == release.StatusPendingRollback {
 				return nil, fmt.Errorf("previous installation (e.g., using vela install or helm upgrade) is still in progress. Please try again in %d minutes", timeoutInMinutes)
 			}
-
 		}
 
 		// merge un-existing values into the values as user-input, because the helm chart upgrade didn't handle the new default values in the chart.
+		// the new default values <= the old custom values <= the new custom values
 		if config.ReuseValues {
 			// sort will sort the release by revision from old to new
 			relutil.SortByRevision(releases)
 			rel := releases[len(releases)-1]
-			// merge new chart values into old values, the values of old chart has the high priority
-			mergedWithNewValues := chartutil.CoalesceTables(rel.Chart.Values, ch.Values)
-			// merge the chart with the released chart config but follow the old config
-			mergeWithConfigs := chartutil.CoalesceTables(rel.Config, mergedWithNewValues)
 			// merge new values as the user input, follow the new user input for --set
-			values = chartutil.CoalesceTables(values, mergeWithConfigs)
+			values = chartutil.CoalesceTables(values, rel.Config)
 		}
 
 		// overwrite existing installation
@@ -161,7 +157,8 @@ func (h *Helper) UpgradeChart(ch *chart.Chart, releaseName, namespace string, va
 		install.Namespace = namespace
 		install.Wait = config.Wait
 		install.Timeout = time.Duration(timeoutInMinutes) * time.Minute
-		install.ReuseValues = config.ReuseValues
+		// use the new default value set.
+		install.ReuseValues = false
 		newRelease, err = install.Run(releaseName, ch, values)
 	}
 	// check if install/upgrade worked
diff --git a/pkg/utils/helm/helm_helper_test.go b/pkg/utils/helm/helm_helper_test.go
index f32f4142f..ad70b2a8a 100644
--- a/pkg/utils/helm/helm_helper_test.go
+++ b/pkg/utils/helm/helm_helper_test.go
@@ -49,7 +49,10 @@ var _ = Describe("Test helm helper", func() {
 		helper := NewHelper()
 		chart, err := helper.LoadCharts("./testdata/autoscalertrait-0.1.0.tgz", nil)
 		Expect(err).Should(BeNil())
-		release, err := helper.UpgradeChart(chart, "autoscalertrait", "default", nil, UpgradeChartOptions{
+		release, err := helper.UpgradeChart(chart, "autoscalertrait", "default", map[string]interface{}{
+			"replicaCount": 2,
+			"image.tag":    "0.1.0",
+		}, UpgradeChartOptions{
 			Config:  cfg,
 			Detail:  false,
 			Logging: util.IOStreams{Out: os.Stdout, ErrOut: os.Stderr},
@@ -58,6 +61,42 @@ var _ = Describe("Test helm helper", func() {
 		crds := GetCRDFromChart(release.Chart)
 		Expect(cmp.Diff(len(crds), 1)).Should(BeEmpty())
 		Expect(err).Should(BeNil())
+		deployments := GetDeploymentsFromManifest(release.Manifest)
+		Expect(cmp.Diff(len(deployments), 1)).Should(BeEmpty())
+		Expect(cmp.Diff(*deployments[0].Spec.Replicas, int32(2))).Should(BeEmpty())
+		containers := deployments[0].Spec.Template.Spec.Containers
+		Expect(cmp.Diff(len(containers), 1)).Should(BeEmpty())
+
+		// add new default value
+		Expect(cmp.Diff(containers[0].Image, "ghcr.io/oam-dev/catalog/autoscalertrait:0.1.0")).Should(BeEmpty())
+
+		chartNew, err := helper.LoadCharts("./testdata/autoscalertrait-0.2.0.tgz", nil)
+		Expect(err).Should(BeNil())
+
+		// the new custom values should override the last release custom values
+		releaseNew, err := helper.UpgradeChart(chartNew, "autoscalertrait", "default", map[string]interface{}{
+			"image.tag": "0.2.0",
+		}, UpgradeChartOptions{
+			Config:      cfg,
+			Detail:      false,
+			ReuseValues: true,
+			Logging:     util.IOStreams{Out: os.Stdout, ErrOut: os.Stderr},
+			Wait:        false,
+		})
+		Expect(err).Should(BeNil())
+		deployments = GetDeploymentsFromManifest(releaseNew.Manifest)
+		Expect(cmp.Diff(len(deployments), 1)).Should(BeEmpty())
+		// keep the custom values
+		Expect(cmp.Diff(*deployments[0].Spec.Replicas, int32(2))).Should(BeEmpty())
+		containers = deployments[0].Spec.Template.Spec.Containers
+		Expect(cmp.Diff(len(containers), 1)).Should(BeEmpty())
+
+		// change the default value
+		Expect(cmp.Diff(containers[0].Image, "ghcr.io/oam-dev/catalog/autoscalertrait:0.2.0")).Should(BeEmpty())
+
+		// add new default value
+		Expect(cmp.Diff(len(containers[0].Env), 1)).Should(BeEmpty())
+		Expect(cmp.Diff(containers[0].Env[0].Name, "env1")).Should(BeEmpty())
 	})
 
 	It("Test UninstallRelease", func() {
diff --git a/pkg/utils/helm/testdata/autoscalertrait-0.1.0.tgz b/pkg/utils/helm/testdata/autoscalertrait-0.1.0.tgz
index 7c2412ac5..3d912de2b 100644
Binary files a/pkg/utils/helm/testdata/autoscalertrait-0.1.0.tgz and b/pkg/utils/helm/testdata/autoscalertrait-0.1.0.tgz differ
diff --git a/pkg/utils/helm/testdata/autoscalertrait-0.2.0.tgz b/pkg/utils/helm/testdata/autoscalertrait-0.2.0.tgz
new file mode 100644
index 000000000..fe77cdf9d
Binary files /dev/null and b/pkg/utils/helm/testdata/autoscalertrait-0.2.0.tgz differ