The invention provides a charging vehicle power supply system based on mixed buses and a control method thereof. The system comprises a three-phase commercial power interface, a vehicle-mounted AC generator, a three-phase AC change-over switch, a rectification device, a battery cluster, an AC-DC integrated charging device, a DC bus, an AC bus, a DC quick charge interface, an AC slow charge interface and a main control cabinet. The three-phase commercial power interface and the vehicle-mounted AC generator are connected with the three-phase AC change-over switch, and then, are connected with the input end of the rectification device; the output end of the rectification device is connected with the battery cluster and the AC-DC integrated charging device; the AC-DC integrated charging device is connected at the two ends of the battery cluster; the AC-DC integrated charging device outputs an AC voltage to the AC bus and outputs a DC voltage to the DC bus; and the main control cabinet is connected with the three-phase AC change-over switch, the rectification device and the AC-DC integrated charging device. The system integrates AC charging and DC charging, is diversified in energy access, is convenient to move, and is not limited by charging sites and vehicle models.