The mechanism of a ripple formation process under swash zone, which is shallower than surf zone, has not yet been fully investigated due to the difficulty of a precise measurement or of an implementation of accurate numerical simulation, under complex boundary conditions caused by wave breakings or bores. To simulate the formation process of the ripples resulting from a sediment transport around swash seabed, the enhanced MPS (moving particle semi-implicit) is employed, which enable simulating wave breakings with a high degree of accuracy. On the other hand, the DEM (distinct element method) is adopted for simulating the ripple formation from tracking individual sand particle. This DEM-MPS coupling model based on particle method will have a high potential to accurately simulate violent flow and its induced sediment transport. The interaction between fluid flow and sediment particles in the formation process of ripples on the swash zone has been numerically examined from the spatial profiles of the flow field and interparticle forces. In this study, the effect of pore water on the formation process of rolling grain ripples is discussed, in particular. Numerical results indicate that the pore water plays an important role in fluidization of sediment DEM particles and contributes development of the ripple formation.