An electronic device displays electronic files on a display device. When a user views the electronic device, a video camera captures a real-time video consisting of a plurality of frames of the user. The electronic device recognizes a face region in each frame and a lip outline in the face region of the frame, and generates a lip shape variation video of a lip of the user according to the lip outline in each frame and a capturing time of each frame. Furthermore, the electronic device searches a preset lip-language video that are pre-stored in a storage device and matches the lip shape variation video, and controls display of the electronic files by executing an voice command associated with the matched preset lip-language video.