The pressure relief valve can release the pressure in the water supply pipe which exceeds the safety setting value of the guide valve, and maintain the pressure in the pipe below the safety setting value, so as to prevent the high pressure or sudden pressure (SURGE) in the pipe from damaging the pipeline or equipment. It can be used for the pressure relief of the fire test circulation system in high-rise buildings to prevent the system from danger caused by excessive water pressure. The pressure relief valve can maintain the upstream water supply pressure in the main valve to be kept below the safety setting value. More than a certain set value to ensure the pressure in the upstream water supply area of the main valve.