A backlight assembly includes a light guide plate, containing a plurality of dots. Each dot includes a first reflecting surface and a second reflecting surface, respectively configured to reflect a first incident light such that reflected light emerges in a first preset direction in a narrow viewing angle mode, and to diffusely reflect a second incident light such that the reflected light emerges dispersedly in a wide viewing angle mode. A first light source can be disposed over a lateral side of the light guide plate and facing the first reflecting surface, to provide the first incident light on the first reflecting surface in the narrow viewing angle mode. A second light source can be disposed over another lateral side of the light guide plate and facing the second reflecting surface to provide the second incident light on the second reflecting surface in the wide viewing angle mode.