Abstract: This paper presents the design principle and scheme for ACPR1000 NPP RPS with a self-diagnosis function, based on Firm Sys, including Firm Sys platform fault diagnosing, diagnostic information transmitting and fault indicating. Test result showed that the self-diagnostic function can successfully transmit and indicate the fault information, as a result of that the self-diagnosis function can supply sufficient information for decision making on routine maintenance and emergency situation for ACPR1000 NPP, to satisfy the specifications, regulations and application requirements in nuclear power industry.