Most of the recent natural disasters such as landslide and tsunamis are complex phenomena in which fluid, ground, structures, etc. affect each other. Therefore, it is necessary to study from various mechanical viewpoints. Among them, in this research, we focus on “soil-water mixed phase flow” where fluid and soil affect each other, such as slope failure and ground collapse. In this study, ISPH method is applied for fluid simulation while DEM is applied for modelling of soil behavior. Then, a general-purpose fluid-solid multiphase flow simulator is developed using the ISPH-DEM coupling method. In addition, in DEM analysis, there are problems in consideration of apparent cohesion related to water content. In our analysis method, in order to adapt to unsaturated ground, the liquid bridge force model proposed in the powder technology field.