看看doc.你需要使用：AVLayerVideoGravityResizeAspectFill@H_301_3@

编辑：@H_301_3@

基于此,提问者创建的解决方案是：@H_301_3@

- (void)setSession:(AVCaptureSession *)session {
    ((AVPlayerLayer *)[self layer]).videoGravity = AVLayerVideoGravityResizeAspectFill;
    ((AVPlayerLayer *)[self layer]).bounds = ((AVPlayerLayer *)[self layer]).bounds;
    [(AVCaptureVideoPreviewLayer *)[self layer] setSession:session];
}