The utility model provides a backlight source of a liquid crystal display (LCD). The backlight source of the LCD comprises light-emitting diode (LED) backlight sources, an aluminum substrate printed circuit board (PCB) and an optical cement protective film. The LED backlight sources are arranged on the aluminum substrate PCB. The surfaces of the LED backlight sources are coated with the optical cement protective film. The backlight source of the LCD is simple in structure, adopts a high heat-conducting aluminum substrate as a base material of the PCB, and reduces thermal-conduction resistance. The optical cement protective film is adopted to be mixed with diffusive substances, and the protective layer is coated on the surfaces of the LED backlight sources. The protective layer is damp-proof and dustproof, and has good insulating performance. When light rays emitted by point light sources formed by the LED backlight sources pass through the protective layer, the light rays cross one another and are diffused to form area light sources with uniform brightness distribution through the scattering effect of the mixed diffusive substances. White LEDs are used as the main light sources, and are supplemented by red LEDs, green LEDs and blue LEDs to carry out color compensation, and then colors with clear chroma are obtained.