A backlight control device adapted to control a plurality of backlight sources is provided. The backlight control device includes a timing control circuitry and a local-dimming control circuitry. The timing control circuitry is configured to generate a transmission packet according to a first customized content specification, where the transmission packet includes control information and brightness information. The timing control circuitry includes a differential circuit, where the differential circuit is configured to transmit the transmission packet according to a differential voltage level. The local-dimming control circuitry includes a receiving circuit electrically coupled to the differential circuit. The receiving circuit is configured to receive the transmission packet. The local-dimming control circuitry is configured to transmit a light source control signal according to the control information and the brightness information.