The invention discloses a vehicle-mounted warning light control system. A warning light includes a plurality of light emitting modules. Each light emitting module includes an LED light source and a drive control module driving the LED light source. A vehicle-mounted signal wire is connected with an input end of a main controller. An output of the main controller is connected with the drive control module of each light emitting module through a cable. The light emitting modules are connected in parallel with one another. The cable includes a power supply wire, a ground wire and the signal wire. The drive control modules are burned with communication addresses, and the communication address of each drive control module is different. The main controller sends a control command with the address to all the drive control modules through the signal wire after signal receiving and processing, and the drive control module corresponding to the address receives the control command and carries out a corresponding action. According to the system, only the three wires are needed to complete connection between the main controller and the light emitting modules through adding the unique communication address to each light emitting module, and wiring of the warning light is greatly simplified.