diff --git a/backend/src/api.rs b/backend/src/api.rs
index 6ff8a2c..75f1ff6 100644
--- a/backend/src/api.rs
+++ b/backend/src/api.rs
@@ -110,7 +110,10 @@ pub async fn preview_cron(
         chrono::Utc::now(),
         request.count,
     )
-    .map_err(|error| ApiError::validation("expression", error.to_string()))?;
+    .map_err(|error| {
+        tracing::debug!(error = %error, "cron preview failed");
+        ApiError::validation("expression", error.user_message())
+    })?;
     Ok(Json(preview))
 }
 
diff --git a/backend/src/cron.rs b/backend/src/cron.rs
index 23a7a74..8635abc 100644
--- a/backend/src/cron.rs
+++ b/backend/src/cron.rs
@@ -21,6 +21,27 @@ pub enum CronPreviewError {
     InvalidTimezone(String),
 }
 
+impl CronPreviewError {
+    /// 面向界面的中文说明。解析器原始错误（英文、带组件路径）只写日志，
+    /// 不再直接抛给前端。
+    pub fn user_message(&self) -> String {
+        match self {
+            Self::InvalidExpression(detail) => {
+                if detail.contains("Invalid step syntax") {
+                    "Cron 表达式步长写法不正确：不要用「0/2」这种单数字步长，通配步长写「*/2」，范围步长写「1-10/2」"
+                        .to_owned()
+                } else {
+                    "Cron 表达式无效，请检查字段取值与步长写法（通配步长用 */n，范围步长用 a-b/n）"
+                        .to_owned()
+                }
+            }
+            Self::TooManyRuns => format!("一次最多预览 {MAX_PREVIEW_RUNS} 次运行"),
+            Self::NoFutureOccurrence => "Cron 表达式没有可计算的未来执行时间".to_owned(),
+            Self::InvalidTimezone(_) => "时区必须是有效的 IANA 时区名称".to_owned(),
+        }
+    }
+}
+
 #[derive(Debug, Deserialize, ToSchema)]
 #[serde(deny_unknown_fields)]
 pub struct CronPreviewRequest {
diff --git a/backend/src/tasks/service.rs b/backend/src/tasks/service.rs
index 1346b3a..9eba333 100644
--- a/backend/src/tasks/service.rs
+++ b/backend/src/tasks/service.rs
@@ -166,14 +166,15 @@ fn validate_common(
     })?;
 
     let cron = Cron::from_str(cron_expression).map_err(|error| {
-        crate::error::ApiError::validation("cron", format!("Cron 表达式无效: {error}"))
+        tracing::debug!(error = %error, "invalid cron expression");
+        let message =
+            crate::cron::CronPreviewError::InvalidExpression(error.to_string()).user_message();
+        crate::error::ApiError::validation("cron", message)
     })?;
     cron.find_next_occurrence(&Utc::now(), false)
         .map_err(|error| {
-            crate::error::ApiError::validation(
-                "cron",
-                format!("Cron 表达式没有可计算的未来执行时间: {error}"),
-            )
+            tracing::debug!(error = %error, "cron has no future occurrence");
+            crate::error::ApiError::validation("cron", "Cron 表达式没有可计算的未来执行时间")
         })?;
 
     Ok(())
diff --git a/frontend/src/App.css b/frontend/src/App.css
index f2e1caf..87f1da4 100644
--- a/frontend/src/App.css
+++ b/frontend/src/App.css
@@ -310,7 +310,17 @@
 }
 
 .cron-preview-error {
+  display: flex;
+  align-items: flex-start;
+  gap: 8px;
   color: var(--su-color-danger);
+  font-size: var(--su-font-size-sm);
+  line-height: var(--su-line-height-sm);
+}
+
+.cron-preview-error i {
+  flex: none;
+  margin-top: 2px;
 }
 
 .env-detector-bar {
diff --git a/frontend/src/components/TaskEditorModal.tsx b/frontend/src/components/TaskEditorModal.tsx
index 021431d..67a8d88 100644
--- a/frontend/src/components/TaskEditorModal.tsx
+++ b/frontend/src/components/TaskEditorModal.tsx
@@ -4,6 +4,7 @@ import {
   Button,
   Checkbox,
   FormField,
+  Icon,
   Input,
   Modal,
   Notice,
@@ -290,7 +291,7 @@ export function TaskEditorModal({
               {...register('cron')}
               className="mono-input"
               placeholder="0 0 2 * * *"
-              aria-invalid={Boolean(errors.cron)}
+              aria-invalid={Boolean(errors.cron) || cronPreview.isError}
             />
           </FormField>
 
@@ -354,9 +355,14 @@ export function TaskEditorModal({
               </Text>
             </div>
           ) : cronPreview.isError ? (
-            <Text size="sm" className="cron-preview-error">
-              {cronPreview.error.message}
-            </Text>
+            <div className="cron-preview-error">
+              <Icon name="warning_line" />
+              <span>
+                {cronPreview.error instanceof ApiRequestError
+                  ? cronPreview.error.message
+                  : '暂时无法计算运行时间，请稍后重试'}
+              </span>
+            </div>
           ) : cronPreview.data?.runs.length ? (
             <div className="cron-run-grid">
               {cronPreview.data.runs.map((run, index) => (