The hidden dangers of logic and electrical design in the realization of reactor power control (RPC) function in project are analyzed. Aiming at the lack of monitoring function for the AC filter (ACF) switching anomaly and parameter anomaly without judgment logic in RPC, a monitoring method of RPC is proposed. The monitoring method conducts logical judgement during initiation, entering normal operation program or fault calculation program. It can realize the functions of abnormal switching analysis and judgment of ACF switching status, validity check of AC voltage, validity check of reactive power, oscillation locking of RPC, etc. Some of the functions are applied in engineering.