Hydrochemical working condition of nuclear power plant relates to the safety, stability and economical operation of the whole plant. In view of radioactive factors, it is very important to analyze, identify and supervise the chemical control working condition. Based on AP1000 cases, this article analyzes issues through elaborating the primary system and the secondary system of nuclear power plant, especially the hydrochemical control of steam generator, and then takes targeted and effective control methods to provide references for the future nuclear power plants.