Disclosed is a vehicle-used power supply system. The vehicle power supply system comprises a storage unit, a bidirectional dc/dc convertor, a dc bus, a controller and a driving module. The bidirectional dc/dc convertor is configured to boost the power stored in the storage unit to a dc bus power. The controller is configured to control the bidirectional dc/dc convertor to operate in a boost mode for driving the motor or in a buck mode for charging the storage unit. The driving module is configured to receive the dc bus power and drive the motor.