Abstract: A novel design of reactor protection system (RPS) based on field programmable gate array(FPGA) is introduced. It is aided by microcontroller to achieve a kind of device diversity. The 2 out of 3 voting mechanism is applied. FPGA modules perform the primary protection functions to accelerate the response speed, and avoid the common mode failures in software programming. Microcontrollers are able to enhence the communication ability and man machine interface(MMI), they also accomplish the secondary protection functions.