A method for displaying an image includes acquiring a data clock signal, acquiring a vertical synchronization signal, generating a backlight driving signal according to the vertical synchronization signal, and displaying the image by using a display system according to the data clock signal, the vertical synchronization signal, and the backlight driving signal. The data clock signal includes a first square wave. The vertical synchronization signal includes a second square wave. No common time interval is between a first time interval corresponding to the first square wave and a second time interval corresponding to the second square wave. The backlight driving signal includes a composite wave synthesized by a third square wave and at least one pulse width modulation signal.