A three-dimensional (3D) display system includes a liquid crystal display and a directional backlight module. The backlight module disposed behind the liquid crystal display includes a light-guide plate, a focusing layer, a left backlight source, a right backlight source, and a first V-shaped micro-grooved and a second V-shaped micro-grooved structures of the light-guide plate. The focusing layer is disposed between the light-guide plate and the liquid crystal display. The 3D display method is to instantly switch on and off the left and the right backlight sources to alternately emit the light from the left side and right side of light-guide plate. By means of the first and the second V-shaped micro-grooved structure, the light transmitted from the light-guide plate is focused by the focusing layer within a particular range of angles and passing through the liquid crystal layer for being alternately projected to form a 3D image.