[Objectives] To study the load change of of the typical section of the high-speed M-boat during the water entry of structure.[Methods] This paper is based on the smooth particle dynamics (SPH) multiphase flow algorithm to simulate the water entry of the flat plate and the blow-flare to verify the accuracy of the algorithm. On this basis, the water entry of the typical cross-sectional structure of the high-speed M-boat speedboat is simulated.[Results] The results show that the simulation results of the water entry of plate and the blow-flare was in good agreement with the test results, which verifies the accuracy of the algorithm; the high-speed M-boat has a second impact during the water entry ; a larger dead-rise angle would make the load of the first impact smaller, but if the dead-rise angle is too large, the impact load on the structure during the second slamming will increase significantly. [Conclusions] The SPH multiphase flow algorithm could simulate the water entry of the high-speed M-boat well; The dead-rise angle of the high-speed M-boat should be appropriate, which provides a valuable reference for the design of the high-speed M-boat.