Based on the moving particle semi implicit method discrete element method(MPS DEM) coupling model, the J ring test of self compacting concrete(SCC) was numerically simulated, the effects of the plastic viscosity, yield strength and density of mortar on the simulation results of SCC J ring test were studied. The results show that the mortars density will not significantly influence the results of the J ring test. The plastic viscosity and yield strength of mortar can affect the expansion flow time and the expansion form. And the sensitivity of mortar yield strength is greater than that of mortar plastic viscosity. With the increase of the mortars plastic viscosity, the flow time of SCC increases, and the filling distance decreases. With the increase of yield strength, the flow time of SCC becomes shorter, and the filling distance decreases with the same viscosity of mortar. The mortar plastic viscosity has a greater impact on the uniformity for the aggregate distribution inside and outside the J ring, and the higher the mortar plastic viscosity, the more uniform the aggregate distribution.