The electric power steering system is applicable to Chang'an 4500 model and is composed of C-EPS steering column pipe assembly, controller, intermediate shaft and harness. The steering column pipe assembly comprises a torque sensor, a power assisted motor and a reduction mechanism. The torque sensor in the system studio converts the driver's steering force into an electrical signal and sends it to the controller. The controller receives the torque signal, engine speed and vehicle speed signal, and controls the operation of the power assisted motor through the control algorithm to realize power assisted steering