The invention provides an electric power steering system. The system comprises a signal acquisition unit, a control unit and an execution unit, wherein the control unit is used for receiving a signal output by the signal acquisition unit in real time, judging whether to enter an active steering mode or an auxiliary steering mode according to the signal, transmitting a command to the execution unit according to the signal and controlling the execution unit to act correspondingly. The invention also provides an automobile using the electric power steering system and a method for controlling the steering of a vehicle based on the electric power steering system. According to the system, the method and the automobile, an auxiliary steering control function, an aligning power control function, an aligning damping control function and other functions of the conventional electric power steering system can be realized, ambient environment information of the vehicle can be detected, and an active steering control function can be realized under an emergent working condition, so that traffic accidents can be effectively prevented.