diff --git a/src/cli/help.ts b/src/cli/help.ts
new file mode 100644
index 0000000..e264631
--- /dev/null
+++ b/src/cli/help.ts
@@ -0,0 +1,138 @@
+interface CommandHelpDef {
+  name: string;
+  alias: string;
+  description: string;
+  usage: string;
+  args: { name: string; desc: string }[];
+  detail: string;
+  examples: string[];
+}
+
+const COMMANDS: Record<string, CommandHelpDef> = {
+  init: {
+    name: "init",
+    alias: "init <工具...>",
+    description: "初始化 Rune 并注入工具配置",
+    usage: "rune init <工具...>",
+    args: [{ name: "<工具...>", desc: "要注入的 AI 工具，如 opencode、claude-code" }],
+    detail: "在当前项目中创建 .rune 目录结构，并注入指定 AI 工具的 command 和 skill 配置文件。",
+    examples: [
+      "rune init opencode",
+      "rune init opencode claude-code",
+    ],
+  },
+  discuss: {
+    name: "discuss",
+    alias: "discuss",
+    description: "讨论：生成讨论阶段提示词",
+    usage: "rune discuss",
+    args: [],
+    detail: "生成 SDD 流程中讨论阶段的提示词，输出到标准输出。需要先运行 rune init 初始化项目。",
+    examples: ["rune discuss"],
+  },
+  plan: {
+    name: "plan",
+    alias: "plan <名称>",
+    description: "规划：生成规划阶段提示词",
+    usage: "rune plan <change-name>",
+    args: [{ name: "<change-name>", desc: "变更名称，如 \"add-login\"" }],
+    detail: "生成规划阶段的提示词。变更目录将创建在 .rune/changes/<change-name>/ 下。",
+    examples: [
+      "rune plan add-user-auth",
+      "rune plan fix-memory-leak",
+    ],
+  },
+  build: {
+    name: "build",
+    alias: "build <名称>",
+    description: "构建：生成构建阶段提示词",
+    usage: "rune build <change-name>",
+    args: [{ name: "<change-name>", desc: "变更名称，如 \"add-login\"" }],
+    detail: "生成构建阶段的提示词。变更目录需已存在（通过 rune plan 创建）。",
+    examples: [
+      "rune build add-user-auth",
+      "rune build fix-memory-leak",
+    ],
+  },
+  archive: {
+    name: "archive",
+    alias: "archive <名称>",
+    description: "归档：归档变更并生成提示词",
+    usage: "rune archive <change-name>",
+    args: [{ name: "<change-name>", desc: "变更名称，如 \"add-login\"" }],
+    detail: "将变更目录从 .rune/changes/ 移动到 .rune/archive/，并生成归档阶段提示词。",
+    examples: [
+      "rune archive add-user-auth",
+      "rune archive fix-memory-leak",
+    ],
+  },
+  status: {
+    name: "status",
+    alias: "status",
+    description: "查看：列出当前进行中的变更",
+    usage: "rune status",
+    args: [],
+    detail: "扫描 .rune/changes/ 目录，列出所有进行中的变更及其任务进度。",
+    examples: ["rune status"],
+  },
+};
+
+export function showGlobalHelp(): string {
+  const lines: string[] = [
+    "Rune — 基于规格驱动开发（SDD）的 AI 开发辅助工具",
+    "",
+    "用法:",
+    "  rune <命令> [参数]",
+    "",
+    "命令:",
+  ];
+
+  const entries = Object.values(COMMANDS);
+  const maxAliasLen = Math.max(...entries.map((c) => c.alias.length));
+  for (const cmd of entries) {
+    lines.push(`  ${cmd.alias.padEnd(maxAliasLen)}   ${cmd.description}`);
+  }
+
+  lines.push(`  ${"help".padEnd(maxAliasLen)}   显示帮助信息`);
+  lines.push(`  ${"version".padEnd(maxAliasLen)}   显示版本号`);
+
+  lines.push("");
+  lines.push("示例:");
+  lines.push("  rune init opencode           初始化并注入 OpenCode 配置");
+  lines.push("  rune plan add-login          开始规划 \"add-login\" 变更");
+  lines.push("  rune status                  查看当前变更状态");
+
+  return lines.join("\n");
+}
+
+export function showCommandHelp(name: string): string | null {
+  const cmd = COMMANDS[name];
+  if (!cmd) return null;
+
+  const lines: string[] = [
+    `rune ${cmd.name} — ${cmd.description}`,
+    "",
+    "用法:",
+    `  ${cmd.usage}`,
+  ];
+
+  if (cmd.args.length > 0) {
+    lines.push("");
+    lines.push("参数:");
+    for (const arg of cmd.args) {
+      lines.push(`  ${arg.name}    ${arg.desc}`);
+    }
+  }
+
+  lines.push("");
+  lines.push("描述:");
+  lines.push(`  ${cmd.detail}`);
+
+  lines.push("");
+  lines.push("示例:");
+  for (const ex of cmd.examples) {
+    lines.push(`  ${ex}`);
+  }
+
+  return lines.join("\n");
+}
diff --git a/tests/cli/help.test.ts b/tests/cli/help.test.ts
new file mode 100644
index 0000000..f5228cb
--- /dev/null
+++ b/tests/cli/help.test.ts
@@ -0,0 +1,50 @@
+import { describe, it, expect } from "bun:test";
+import { showGlobalHelp, showCommandHelp } from "../../src/cli/help.ts";
+
+describe("showGlobalHelp", () => {
+  it("包含所有命令行", () => {
+    const output = showGlobalHelp();
+    expect(output).toContain("rune <命令> [参数]");
+    expect(output).toContain("init <工具...>");
+    expect(output).toContain("discuss");
+    expect(output).toContain("plan <名称>");
+    expect(output).toContain("build <名称>");
+    expect(output).toContain("archive <名称>");
+    expect(output).toContain("status");
+    expect(output).toContain("help");
+    expect(output).toContain("version");
+  });
+
+  it("包含示例", () => {
+    const output = showGlobalHelp();
+    expect(output).toContain("rune init opencode");
+    expect(output).toContain("rune plan add-login");
+    expect(output).toContain("rune status");
+  });
+
+  it("以标题行开头", () => {
+    const output = showGlobalHelp();
+    expect(output.startsWith("Rune")).toBe(true);
+  });
+});
+
+describe("showCommandHelp", () => {
+  it("plan 命令包含用法、参数、描述、示例", () => {
+    const output = showCommandHelp("plan");
+    expect(output).toContain("rune plan <change-name>");
+    expect(output).toContain("<change-name>");
+    expect(output).toContain("规划阶段");
+    expect(output).toContain("rune plan add-user-auth");
+  });
+
+  it("init 命令包含工具参数说明", () => {
+    const output = showCommandHelp("init");
+    expect(output).toContain("rune init <工具...>");
+    expect(output).toContain("opencode");
+  });
+
+  it("不存在的命令返回 null", () => {
+    const output = showCommandHelp("nonexistent");
+    expect(output).toBeNull();
+  });
+});