A 3D display device and a driving method thereof are disclosed. The 3D display device comprises a grating and a display panel, and the grating is divided into a bright grating cell and a dark grating cell, the grating comprising a substrate and a plurality of OLED light-emitting devices arranged on the substrate. At least a part of the plurality of OLED light emitting devices emit light to apply the operating voltage to form the bright grating cells, and the non-light emitting OLED light-emitting devices form the dark grating cells. The 3D display device is for displaying a 3D picture.