Abstract: Compared with the mesh method, the moving particle semi-implicit (MPS) method does not have the problem of mesh distortion, and has unique advantages in capturing the movement of free surface, change of phase state, solid deformation and so on. In order to apply the moving particle semi-implicit method to the simulation of the migration behavior of discrete solids entrained by melts in a serious nuclear reactor core melting accident, a fluid-solid coupling model needs to be established. Within the framework of moving particle semi-implicit method in this paper, the idea of discrete element method (DEM) was coupled, the stability of calculation was improved by introducing a multiphase viscosity model on the fluid-solid coupling interface, and a fluid-solid coupling model suitable for simulating the movement of fluid entrained discrete solids was built. The reliability of the model analysis of discrete solid motion was verified by a solid landslide example. The dimensionless moving distance of the front of the solid landslide was quantitatively compared. The relative error between the experiment and simulation is no more than 6.3%. The reliability of the model analysis of fluid-solid coupling problem was verified by an underwater solid landslide example. The moving distance of the landslide front was quantitatively compared. The relative error between the experiment and simulation is no more than 8.6%. The fluid-solid coupling model established in this paper is suitable for the analysis and simulation of fluid entrained discrete solid motion. The model has good accuracy and stability, and can be used in practical engineering problems.