diff --git a/embed/templates/scripts/run_prometheus.sh.tpl b/embed/templates/scripts/run_prometheus.sh.tpl
index b9d65b516b..3cc9cc591e 100644
--- a/embed/templates/scripts/run_prometheus.sh.tpl
+++ b/embed/templates/scripts/run_prometheus.sh.tpl
@@ -55,5 +55,10 @@ exec bin/prometheus/prometheus \
 {{- end}}
 {{- end}}
 {{- if not .EnablePromAgentMode}}
-    --storage.tsdb.retention="{{.Retention}}"
+{{- if .RetentionSize}}
+    --storage.tsdb.retention.size="{{.RetentionSize}}"
+{{- end}}
+{{- if .RetentionTime}}
+    --storage.tsdb.retention.time="{{.RetentionTime}}"
+{{- end}}
 {{- end}}
diff --git a/pkg/cluster/spec/monitoring.go b/pkg/cluster/spec/monitoring.go
index e295dfa1e3..9386344ca9 100644
--- a/pkg/cluster/spec/monitoring.go
+++ b/pkg/cluster/spec/monitoring.go
@@ -30,6 +30,7 @@ import (
 	"github.com/pingcap/tiup/pkg/cluster/ctxt"
 	"github.com/pingcap/tiup/pkg/cluster/template/config"
 	"github.com/pingcap/tiup/pkg/cluster/template/scripts"
+	logprinter "github.com/pingcap/tiup/pkg/logger/printer"
 	"github.com/pingcap/tiup/pkg/meta"
 	"github.com/pingcap/tiup/pkg/set"
 	"github.com/pingcap/tiup/pkg/utils"
@@ -54,7 +55,9 @@ type PrometheusSpec struct {
 	RemoteConfig          Remote                 `yaml:"remote_config,omitempty" validate:"remote_config:ignore"`
 	ExternalAlertmanagers []ExternalAlertmanager `yaml:"external_alertmanagers" validate:"external_alertmanagers:ignore"`
 	PushgatewayAddrs      []string               `yaml:"pushgateway_addrs,omitempty" validate:"pushgateway_addrs:ignore"`
-	Retention             string                 `yaml:"storage_retention,omitempty" validate:"storage_retention:editable"`
+	Retention             string                 `yaml:"storage_retention,omitempty" validate:"storage_retention:editable"` // deprecated
+	RetentionSize         string                 `yaml:"storage_retention_size,omitempty" validate:"storage_retention_size:editable"`
+	RetentionTime         string                 `yaml:"storage_retention_time,omitempty" validate:"storage_retention_time:editable"`
 	ResourceControl       meta.ResourceControl   `yaml:"resource_control,omitempty" validate:"resource_control:editable"`
 	Arch                  string                 `yaml:"arch,omitempty"`
 	OS                    string                 `yaml:"os,omitempty"`
@@ -270,7 +273,6 @@ func (i *MonitorInstance) InitConfig(
 	cfg := &scripts.PrometheusScript{
 		Port:                spec.Port,
 		WebExternalURL:      fmt.Sprintf("http://%s", utils.JoinHostPort(spec.Host, spec.Port)),
-		Retention:           getRetention(spec.Retention),
 		EnableNG:            spec.NgPort > 0,
 		EnablePromAgentMode: spec.EnablePromAgentMode, // Get from spec directly
 
@@ -282,6 +284,14 @@ func (i *MonitorInstance) InitConfig(
 
 		AdditionalArgs: spec.AdditionalArgs,
 	}
+	// Set retention policy
+	logPtr := ctx.Value(logprinter.ContextKeyLogger).(*logprinter.Logger)
+	if spec.RetentionTime == "" { // keep backward compatiability
+		cfg.RetentionTime = getRetentionTime(logPtr, spec.Retention)
+	} else {
+		cfg.RetentionTime = getRetentionTime(logPtr, spec.RetentionTime)
+	}
+	cfg.RetentionSize = getRetentionSize(logPtr, spec.RetentionSize)
 
 	// Check if agent mode is enabled in additional arguments
 	if !cfg.EnablePromAgentMode {
@@ -675,9 +685,25 @@ func mergeAdditionalScrapeConf(source string, addition map[string]any) error {
 	return utils.WriteFile(source, bytes, 0644)
 }
 
-func getRetention(retention string) string {
+func getRetentionSize(l *logprinter.Logger, retention string) string {
+	retention = strings.ToUpper(strings.TrimSpace(retention))
+	valid, _ := regexp.MatchString("^[1-9]\\d*(B|KB|MB|GB|TB|PB|EB)$", retention)
+	if retention == "" || !valid {
+		if !valid && l != nil {
+			l.Warnf("invalid retention size %s, ignored.", retention)
+		}
+		return ""
+	}
+	return retention
+}
+
+func getRetentionTime(l *logprinter.Logger, retention string) string {
+	retention = strings.TrimSpace(retention)
 	valid, _ := regexp.MatchString("^[1-9]\\d*d$", retention)
 	if retention == "" || !valid {
+		if !valid && l != nil {
+			l.Warnf("invalid retention time %s, using 30d as default", retention)
+		}
 		return "30d"
 	}
 	return retention
diff --git a/pkg/cluster/spec/monitoring_test.go b/pkg/cluster/spec/monitoring_test.go
index 6d3a33addf..ce8b34e355 100644
--- a/pkg/cluster/spec/monitoring_test.go
+++ b/pkg/cluster/spec/monitoring_test.go
@@ -229,32 +229,68 @@ scrape_configs:
 
 func TestGetRetention(t *testing.T) {
 	var val string
-	val = getRetention("-1d")
+	val = getRetentionTime(nil, "-1d")
 	assert.EqualValues(t, "30d", val)
 
-	val = getRetention("0d")
+	val = getRetentionTime(nil, "0d")
 	assert.EqualValues(t, "30d", val)
 
-	val = getRetention("01d")
+	val = getRetentionTime(nil, "01d")
 	assert.EqualValues(t, "30d", val)
 
-	val = getRetention("1dd")
+	val = getRetentionTime(nil, "1dd")
 	assert.EqualValues(t, "30d", val)
 
-	val = getRetention("*1d")
+	val = getRetentionTime(nil, "*1d")
 	assert.EqualValues(t, "30d", val)
 
-	val = getRetention("1d ")
-	assert.EqualValues(t, "30d", val)
+	val = getRetentionTime(nil, "1d ")
+	assert.EqualValues(t, "1d", val)
+
+	val = getRetentionTime(nil, " 1d")
+	assert.EqualValues(t, "1d", val)
 
-	val = getRetention("ddd")
+	val = getRetentionTime(nil, "ddd")
 	assert.EqualValues(t, "30d", val)
 
-	val = getRetention("60d")
+	val = getRetentionTime(nil, "60d")
 	assert.EqualValues(t, "60d", val)
 
-	val = getRetention("999d")
+	val = getRetentionTime(nil, "999d")
 	assert.EqualValues(t, "999d", val)
+
+	val = getRetentionSize(nil, "-1MB")
+	assert.EqualValues(t, "", val)
+
+	val = getRetentionSize(nil, "30d")
+	assert.EqualValues(t, "", val)
+
+	val = getRetentionSize(nil, "1k")
+	assert.EqualValues(t, "", val)
+
+	val = getRetentionSize(nil, "01G")
+	assert.EqualValues(t, "", val)
+
+	val = getRetentionSize(nil, "233mb")
+	assert.EqualValues(t, "233MB", val)
+
+	val = getRetentionSize(nil, "*1GB")
+	assert.EqualValues(t, "", val)
+
+	val = getRetentionSize(nil, "20GB ")
+	assert.EqualValues(t, "20GB", val)
+
+	val = getRetentionSize(nil, " 20GB")
+	assert.EqualValues(t, "20GB", val)
+
+	val = getRetentionSize(nil, "3TB")
+	assert.EqualValues(t, "3TB", val)
+
+	val = getRetentionSize(nil, "30GB")
+	assert.EqualValues(t, "30GB", val)
+
+	val = getRetentionSize(nil, "1EB")
+	assert.EqualValues(t, "1EB", val)
 }
 
 // TestHandleRemoteWrite verifies that remote write configurations are properly handled
diff --git a/pkg/cluster/template/scripts/monitoring.go b/pkg/cluster/template/scripts/monitoring.go
index 2e40e38bd4..3bdec0f439 100644
--- a/pkg/cluster/template/scripts/monitoring.go
+++ b/pkg/cluster/template/scripts/monitoring.go
@@ -26,7 +26,8 @@ import (
 type PrometheusScript struct {
 	Port                int
 	WebExternalURL      string
-	Retention           string
+	RetentionSize       string
+	RetentionTime       string
 	EnableNG            bool
 	EnablePromAgentMode bool
 
diff --git a/pkg/cluster/template/scripts/monitoring_test.go b/pkg/cluster/template/scripts/monitoring_test.go
index c2b2f664b2..f11e8df6d4 100644
--- a/pkg/cluster/template/scripts/monitoring_test.go
+++ b/pkg/cluster/template/scripts/monitoring_test.go
@@ -32,7 +32,8 @@ func TestPrometheusScriptWithAgentMode(t *testing.T) {
 	script := &PrometheusScript{
 		Port:                9090,
 		WebExternalURL:      "http://localhost:9090",
-		Retention:           "30d",
+		RetentionTime:       "30d",
+		RetentionSize:       "100GB",
 		EnableNG:            false,
 		EnablePromAgentMode: true,
 		DeployDir:           "/deploy",