The invention relates to a high and low voltage combined start control method for a vehicle. The combined start control method is as follows: firstly turning on three switches of a main power supply, a low voltage power supply and a high voltage power supply, judging the state of the switches, high voltage powered state, high voltage, current gear and rotating speed, and starting an engine for finishing the whole combined start control method. The high and low voltage combined start of hybrid power supply system can be finished, the starter and the electric generator are protected, the start fault is effectively reduced, the service life of the storage battery is increased, the potential safety hazard of the circuit of the whole vehicle is reduced and the safe and reliable start for the vehicle is ensured.