A display device and a method for displaying an image thereof are disclosed. The display device includes a display panel, a gray scale voltage output circuit, a common voltage output circuit and a control circuit. The display panel, according to a first gray scale voltage signal and a first common voltage signal, display an image; the control circuit is used for controlling the gray scale voltage output circuit and the common voltage output circuit to output a second gray scale voltage signal and a second common voltage to the display panel when at a predetermined time to display another image. The present invention can cause the blink rate to be maintained over time at a relatively stable range.