Abstract:A solution to reduce water hammer pressure was put forward, which realized fast shutting and slowly-closing process of check valve owing to the buffer cylinder, by aimed at the problem of serious closing of check valve of water hammer caused by the pump unexpected stopping. The buffered process of cylinder was theoretically analyzed, and validated with simulation by AMESim software. The results show that the water hammer pressure is proportional to changing of velocity of flow, and the pressure in pipes can be limited in a permitted range, due to slowly-closing process of check valve which reduces the increasing of velocity of flow by the buffer cylinder.