diff --git a/src/App.jsx b/src/App.jsx
index 6e9e216..fce2a15 100644
--- a/src/App.jsx
+++ b/src/App.jsx
@@ -7,6 +7,7 @@ import { ComparisonControls } from './components/ComparisonControls';
 import { Header } from './components/Header';
 import { FileConfigModal } from './components/FileConfigModal';
 import { PanelLeftClose, PanelLeftOpen } from 'lucide-react';
+import { mergeFilesWithReplacement } from './utils/mergeFiles.js';
 
 function App() {
   const [uploadedFiles, setUploadedFiles] = useState([]);
@@ -54,7 +55,7 @@ function App() {
         }
       }
     }));
-    setUploadedFiles(prev => [...prev, ...filesWithDefaults]);
+    setUploadedFiles(prev => mergeFilesWithReplacement(prev, filesWithDefaults));
   }, [globalParsingConfig]);
 
   // 全局文件处理函数
diff --git a/src/components/ChartContainer.jsx b/src/components/ChartContainer.jsx
index aa316e3..d2f9365 100644
--- a/src/components/ChartContainer.jsx
+++ b/src/components/ChartContainer.jsx
@@ -13,6 +13,7 @@ import {
   Legend,
 } from 'chart.js';
 import zoomPlugin from 'chartjs-plugin-zoom';
+import { getMinSteps } from "../utils/getMinSteps.js";
 
 ChartJS.register(
   CategoryScale,
@@ -164,6 +165,17 @@ export default function ChartContainer({
     onMaxStepChange(maxStep);
   }, [parsedData, onMaxStepChange]);
 
+  useEffect(() => {
+    const minSteps = getMinSteps(parsedData);
+    if (minSteps > 0) {
+      onXRangeChange(prev => {
+        const next = { min: 0, max: minSteps - 1 };
+        if (prev.min === next.min && prev.max === next.max) return prev;
+        return next;
+      });
+    }
+  }, [parsedData, onXRangeChange]);
+
   const colors = ['#ef4444', '#3b82f6', '#10b981', '#f59e0b', '#8b5cf6', '#f97316'];
   const createChartData = dataArray => ({
     datasets: dataArray.map((item, index) => {
diff --git a/src/utils/__tests__/getMinSteps.test.js b/src/utils/__tests__/getMinSteps.test.js
new file mode 100644
index 0000000..79c4ab8
--- /dev/null
+++ b/src/utils/__tests__/getMinSteps.test.js
@@ -0,0 +1,20 @@
+import { describe, it, expect } from 'vitest';
+import { getMinSteps } from '../getMinSteps.js';
+
+describe('getMinSteps', () => {
+  it('returns minimum length among enabled files', () => {
+    const parsed = [
+      { enabled: true, metricsData: { a: [{},{},{}], b: [{},{}] } },
+      { enabled: true, metricsData: { a: [{},{},{} ,{}], b: [{},{} ,{}] } },
+    ];
+    expect(getMinSteps(parsed)).toBe(3);
+  });
+
+  it('ignores disabled files', () => {
+    const parsed = [
+      { enabled: false, metricsData: { a: [{},{},{}] } },
+      { enabled: true, metricsData: { a: [{},{}] } }
+    ];
+    expect(getMinSteps(parsed)).toBe(2);
+  });
+});
diff --git a/src/utils/__tests__/mergeFiles.test.js b/src/utils/__tests__/mergeFiles.test.js
new file mode 100644
index 0000000..840440d
--- /dev/null
+++ b/src/utils/__tests__/mergeFiles.test.js
@@ -0,0 +1,20 @@
+import { describe, it, expect } from 'vitest';
+import { mergeFilesWithReplacement } from '../mergeFiles.js';
+
+describe('mergeFilesWithReplacement', () => {
+  it('replaces file with same name and keeps config', () => {
+    const prev = [{ name: 'log1.txt', id: '1', enabled: true, config: { a: 1 }, content: 'old' }];
+    const newFile = { name: 'log1.txt', id: '2', enabled: true, config: {}, content: 'new' };
+    const result = mergeFilesWithReplacement(prev, [newFile]);
+    expect(result).toHaveLength(1);
+    expect(result[0].content).toBe('new');
+    expect(result[0].config).toEqual({ a: 1 });
+  });
+
+  it('adds new file when name does not exist', () => {
+    const prev = [{ name: 'log1.txt', id: '1', enabled: true, config: {}, content: 'old' }];
+    const newFile = { name: 'log2.txt', id: '2', enabled: true, config: {}, content: 'new' };
+    const result = mergeFilesWithReplacement(prev, [newFile]);
+    expect(result).toHaveLength(2);
+  });
+});
diff --git a/src/utils/getMinSteps.js b/src/utils/getMinSteps.js
new file mode 100644
index 0000000..9ae22f2
--- /dev/null
+++ b/src/utils/getMinSteps.js
@@ -0,0 +1,10 @@
+export function getMinSteps(parsedFiles = []) {
+  const enabled = parsedFiles.filter(f => f.enabled !== false);
+  if (enabled.length === 0) return 0;
+  const lengths = enabled.map(file => {
+    const datasets = Object.values(file.metricsData || {});
+    if (datasets.length === 0) return 0;
+    return datasets.reduce((m, d) => Math.max(m, d.length), 0);
+  });
+  return Math.min(...lengths);
+}
diff --git a/src/utils/mergeFiles.js b/src/utils/mergeFiles.js
new file mode 100644
index 0000000..b48f6b3
--- /dev/null
+++ b/src/utils/mergeFiles.js
@@ -0,0 +1,13 @@
+export function mergeFilesWithReplacement(prevFiles, newFiles) {
+  const updated = [...prevFiles];
+  newFiles.forEach(file => {
+    const idx = updated.findIndex(f => f.name === file.name);
+    if (idx !== -1) {
+      const existing = updated[idx];
+      updated[idx] = { ...file, enabled: existing.enabled, config: existing.config };
+    } else {
+      updated.push(file);
+    }
+  });
+  return updated;
+}