The invention relates to a backlight source which comprises a lamp assembly used for providing light for the backlight source, an ultraviolet lamp assembly that is adjacent to the lamp assembly and used for providing ultraviolet, and a control switch, wherein the control switch is arranged outside the backlight source, is connected with the ultraviolet assembly and is used for controlling the off and on of the ultraviolet assembly. The backlight source is provided with the ultraviolet assembly at the position adjacent to the lamp assembly in the backlight source, which can change the irradiation dose of ultraviolet light at the inner side of a liquid crystal panel according to the practical use environment of the liquid crystal display, and avoids the after image phenomena of the liquid crystal display.