diff --git a/lib/cmd/cov.js b/lib/cmd/cov.js
index e8c96b4a..41e73814 100644
--- a/lib/cmd/cov.js
+++ b/lib/cmd/cov.js
@@ -22,6 +22,10 @@ class CovCommand extends Command {
         description: 'istanbul coverage ignore, one or more fileset patterns',
         type: 'string',
       },
+      prerequire: {
+        description: 'prerequire files for coverage instrument',
+        type: 'boolean',
+      },
     };
 
     // you can add ignore dirs here
@@ -44,6 +48,11 @@ class CovCommand extends Command {
   * run(context) {
     const { cwd, argv, execArgv, env } = context;
 
+    if (argv.prerequire) {
+      env.EGG_BIN_PREREQUIRE = 'true';
+    }
+    delete argv.prerequire;
+
     // ignore coverage
     if (argv.x) {
       if (Array.isArray(argv.x)) {
@@ -99,13 +108,6 @@ class CovCommand extends Command {
   getCovArgs(context) {
     let covArgs = [
       // '--show-process-tree',
-      // instrument all files in nyc process and cache to disk,
-      // Then in mocha process, read instrumented files from cache.
-      //
-      // nyc
-      //  `- egg-bin test
-      //    `- mocha
-      '--all',
       '--temp-directory', './node_modules/.nyc_output',
       '-r', 'text-summary',
       '-r', 'json-summary',
diff --git a/test/lib/cmd/cov.test.js b/test/lib/cmd/cov.test.js
index 0ab95084..e7ce0d39 100644
--- a/test/lib/cmd/cov.test.js
+++ b/test/lib/cmd/cov.test.js
@@ -148,4 +148,21 @@ describe('test/lib/cmd/cov.test.js', () => {
       .expect('code', 0)
       .end();
   });
+
+  it('should set EGG_BIN_PREREQUIRE', function* () {
+    const cwd = path.join(__dirname, '../../fixtures/prerequire');
+    yield coffee.fork(eggBin, [ 'cov' ], { cwd })
+      // .debug()
+      .coverage(false)
+      .expect('stdout', /EGG_BIN_PREREQUIRE undefined/)
+      .expect('code', 0)
+      .end();
+
+    yield coffee.fork(eggBin, [ 'cov', '--prerequire' ], { cwd })
+      // .debug()
+      .coverage(false)
+      .expect('stdout', /EGG_BIN_PREREQUIRE true/)
+      .expect('code', 0)
+      .end();
+  });
 });