The invention discloses a display device and a display method thereof. The display device includes a liquid crystal display panel and a backlight module, wherein the liquid crystal display panel comprises a plurality of pixels, each pixel includes three colorful sub-pixels capable of displaying full colors and one white sub-pixel capable of displaying black and white colors, and the three colorful sub-pixels capable of displaying the full colors define a first color gamut space. The backlight module includes a first backlight source and a second backlight source, wherein the light emitted by the first backlight source is white, and the colors of the light emitted by the second backlight source are located outside the first color gamut space. The display device can be applied to the occasion having the demand of low power consumption, can be also applied to the occasion having the demand for high color expression and accordingly has better practicability.