Abstract:  In order to make use of the advantages of different types of controllers, based on the fuzzy multi-model of reactor core, a fuzzy switching controller is designed by using PID controller and fuzzy controller with the T-S fuzzy rules. Taking the pressurized water reactor core of the Three Mile Island nuclear power plant as an example, a fuzzy switching control system for reactor core power is developed and the simulation studies are carried out. The results show that the designed core fuzzy switching controller is more suitable for the core power control under the core reactivity step disturbance and core inlet coolant temperature step disturbance than the traditional PID controller.