In the loop network layout of the subway fire hydrant system, the fire water supply facilities in all stations and sections shall be integrated with each other so that the fire water sources at each station are used as backup to improve the reliability of the fire hydrant system. In order to analyze the fire protection policy of the loop network layout, the hydraulic calculation model is first used to simulate the automatic start of pressure in the fire hydrant system in the subway. Multiple conditions are calculated for the system operation process to simulate the starting conditions of the fire pump in the fire pipe network under different fire points, different elevation, different pressure stabilizing values of the pressure-stabilizing pump and accident conditions. According to the simulation results, it is proved that the loop network layout method can start the main fire pump automatically according to the pressure change of the pipe network. Combined with the characteristics of the loop network layout, the design and operational recommendations of the loop network fire hydrant system layout are proposed.