In-service inspection(ISI) is an important method to ensure the safety of the mechanical equipments in nuclear power stations. According to the in-service inspection experience feedback from the domestic nuclear power stations, the reasonableness of some provisions in the RSE-M code are discussed and the applications of risk-informed in-service inspection(RI-ISI)are introduced, and the advices for the optimization of the ISI of the domestic M310 nuclear power stations are proposed.