A system for preventing lane deviation of a vehicle is provided. The system comprises a lane detecting device, a running condition detecting device, a deviation judging device, and a vehicle behavior control device. The vehicle behavior control device controls a behavior of the vehicle so as to generate a yaw moment in the direction to prevent the vehicle from deviating from the running lane. The lane detecting device detects the running lane based on a variation in a running direction of the vehicle due to the yaw moment generated by the vehicle behavior control device. A method for preventing lane deviation of a vehicle is also provided.