The invention belongs to the field of photo-electricity display and relates to an energy-saving display device and display method. The display device comprises an upper light-transmitting protecting layer and a lower light-transmitting protecting layer. The portion under the upper protecting layer is plated with two layers of films. The two layers are a conducting film-plated layer and a photosensitive layer in sequence. The lower protecting layer is plated with a conducting film-plated layer. An electrochromism layer, an ionic conducting layer and an ion storing layer are sequentially arranged under the photosensitive layer. The conducting film-plated layer on the upper protecting layer and the conducting film-plated layer on the lower protecting layer are connected with extraction electrodes for being connected with a drive power source. After electrochemistry exposure and electricity development are carried out through certain steps, the display device will display content endowed by an external light source, and the content does not need to be maintained by power supply. The display device has the advantages of saving energy, and being easy to manufacture and maintain and low in cost.