diff --git a/frontend/src/i18n/locales/en/collectors.ts b/frontend/src/i18n/locales/en/collectors.ts
index d7b88f7..d4b6a32 100644
--- a/frontend/src/i18n/locales/en/collectors.ts
+++ b/frontend/src/i18n/locales/en/collectors.ts
@@ -78,6 +78,9 @@ const collectors = {
     cluster: 'Target Cluster',
     clusterPlaceholder: 'Select a cluster',
     namespace: 'Namespace',
+    namespaceHintSidecar: 'The namespace where the TARGET Deployment lives. The platform finds that Deployment there and injects a Fluent Bit sidecar; collected logs also carry this namespace label. It is NOT a log filter.',
+    namespaceHintDaemonset: 'The namespace where the Promtail DaemonSet is deployed. The DaemonSet collects container logs from ALL namespaces in the cluster — it does not filter by namespace (usually just the Loki namespace, e.g. log).',
+    namespaceHintHost: 'Not used in host mode.',
     nsPickCluster: 'Select a cluster first',
     nsLoading: 'Loading namespaces…',
     nsPick: 'Select a namespace',
diff --git a/frontend/src/i18n/locales/zh/collectors.ts b/frontend/src/i18n/locales/zh/collectors.ts
index 28592aa..83b740b 100644
--- a/frontend/src/i18n/locales/zh/collectors.ts
+++ b/frontend/src/i18n/locales/zh/collectors.ts
@@ -82,6 +82,9 @@ const collectors = {
     cluster: '目标集群',
     clusterPlaceholder: '选择集群',
     namespace: '命名空间',
+    namespaceHintSidecar: '填「目标应用（Deployment）所在的命名空间」。平台会在该命名空间里找到目标 Deployment 并注入 Fluent Bit sidecar，采集到的日志也会打上这个 namespace 标签。它不是日志过滤条件。',
+    namespaceHintDaemonset: '填「Promtail DaemonSet 部署到哪个命名空间」。DaemonSet 会采集整个集群所有命名空间的容器日志，不按命名空间过滤（一般就用 Loki 所在的 log）。',
+    namespaceHintHost: '主机模式不使用该字段。',
     nsPickCluster: '先选择集群',
     nsLoading: '加载命名空间…',
     nsPick: '选择命名空间',
diff --git a/frontend/src/pages/collectors/components/CollectorFormDialog.tsx b/frontend/src/pages/collectors/components/CollectorFormDialog.tsx
index 3342b93..aa39460 100644
--- a/frontend/src/pages/collectors/components/CollectorFormDialog.tsx
+++ b/frontend/src/pages/collectors/components/CollectorFormDialog.tsx
@@ -389,6 +389,15 @@ export const CollectorFormDialog = memo(function CollectorFormDialog({
                           )}
                         </FormControl>
                         <FormMessage />
+                        {/* 这个字段在不同采集类型下含义完全不同，必须写清楚，
+                            否则用户会以为它是"日志过滤条件"。 */}
+                        <p className="mt-1 min-h-4 text-xs text-muted-foreground">
+                          {isSidecarType
+                            ? t('form.namespaceHintSidecar')
+                            : collectorType === 'k8s-daemonset'
+                              ? t('form.namespaceHintDaemonset')
+                              : t('form.namespaceHintHost')}
+                        </p>
                         {isSidecarType && <div className="flex items-center gap-2 text-xs">
                           <Button type="button" variant="link" size="sm" className="h-auto p-0" onClick={() => setManualNamespace((value) => !value)}>
                             {manualNamespace ? t('form.pickFromCluster') : t('form.manualInput')}