A 3D display device and a driving method thereof are disclosed. The 3D display device includes a backlight module, a liquid crystal display (LCD) panel and a control module; the backlight module includes a light guide plate (LGP) and a plurality of light sources; light emitted by the plurality of light sources is at least partially incident into the LGP; a plurality of grating pixels are disposed on a surface at a light-existing side of the LGP; the LCD panel includes a plurality of light-adjusting pixels; and the control module is connected with the backlight module and the LCD panel, and configured to drive the plurality of light sources to be lit sequentially or simultaneously within a time period of one frame and adjust a gray scale of each light-adjusting pixel in the LCD panel in a time period of lighting each light source.