The invention discloses a multi-
mode switching control method and 
system of an 
electric power steering system. The method comprises the following steps that (S1), a vehicle 
steering wheel torque and rotary angle and vehicle speed information are obtained, and a 
control mode is selected; (S2), a fuzzy switching controller is designed, and the output current is worked out according to the target current and the 
weight coefficient; (S3), the differential and the second-order differential of the output current are calculated, an 
extension set relevant to the feature state is built, and regional division is conducted; and (S4), the fuzzy switching controller is subjected to functional improvement on the basis of an 
extension theory, different control methods are set in different regions of the 
extension set, the 
correlation function is built, the condition that the output current locates in which region of the 
extension set is judged, and the optimized 
electricity quantity is input into a motor. According to the multi-
mode switching control method and 
system of the 
electric power steering system, the target current is optimized according to different adopted control strategies at different current set states, so that the better control property is obtained, and EPS multi-mode smooth switching is achieved.