In high speed planing, the scale of free surface deformation and extended spray become comparable to the ship length. In numerical approaches of the problem, some difficulties arise from the mesh generation around the large, irregular formation of the free surface. One of its alternative approaches is the particle based computational fluid dynamics. The present authors applied the Moving Particle Semi-implicit (MPS) method originally developed by Koshizuka¹⁾ to the problem of high-speed planing. This paper describes the modifications to the MPS method to solve the problem, and shows numerical results of spray formation around a wedged cylindrical model.