In order to improve the reverse impact characteristics of large-flow pilot-operated check valve at opening, reducing vibration, cavitations and unloading time, three different main poppets are selected. Setting impact pressure for 30 MPa, flow for 1 000 L/min as the basic parameters, the cavitations phenomenon was explored based on the analysis of gasliquid two-phase flow by Fluent software, and then conducted the experimental verification. Meanwhile the dynamic characteristic of different pilotoperated check valve was studied by the impact test system. The simulation results show that the fluid pressure decreases obviously while flowing through poppet area. And the sudden decreasing of flow area at the orifice port of poppet results in the increasing of flow-velocity because of which the cavitations area appears on the side of main poppet. And stepped throttling structure can effectively reduce the cavitations area, decreasing the generation of cavitations. The experimental results show that pressure vibration of stepped main poppet is significantly reduced during process of unloading, for 28.41 MPa, flow rise gradient for 4.86×105 L/min2, unloading time for 711 ms, indicating it is opened more rapidly and dynamic performance is more superior. At the same time, the conclusion indicates that stepped throttling structure can effectively reduce the pressure vibration of pilot-operated check valve during process of unloading, improve response speed and enhance the impact properties, and reduce cavitations, which verified the correctness of simulation and the rationality of cavitations index.