Abstract: Based on operational safety analysis of marine nuclear power, a general two-phase flow simulation model for nuclear secondary loop system was established, which can fit the needs of real-time dynamic simulation of complex two-phase fluid networks under manual intervention conditions, and expand the reach field of current general safety analysis program of nuclear power plant. As an example, the capability of the simulation model was validated by taking simulation of rapidly power reducing condition of secondary loop. The results indicate that the model reflects the dynamic characteristics of secondary loop system of marine nuclear power properly, and can be used to validate the accident treatment regulation and function of control system. The model can also fit the needs of developing saturated steam system simulation software of nuclear power station.