Rubble spur dike is a common hydraulic structure used in water regulation whose hydrodynamics characteristics of the spur is an important reference to related engineering assessment. Fluid-solid coupling model is a powerful tool used to simulate corresponding hydrodynamic process and describe the mechanical characteristics. A CFD-DEM numerical model is established，which is a coupling of water flow model in a porous medium with free surface and discrete element method. The validity and simulation accuracy of the model are verified based on experimental data. Using this numerical model，the numerical simulation of the flow around the rubble spur dike is carried out，and the influence of the structural water permeability on the local flow and the force of the rubble body is studied. The results show that：1）As the water permeability of the spur dike increases，the wake area extends along the flow direction. 2）The velocity distributions of the main flow zone and the wake zone under different water permeability conditions of the dam body are obviously different，but the shear velocity distribution in the wake zone has a certain similarity. 3）The force analysis of the spur dike structure shows that as the water permeability of the dike body increases，the force area of the block spreads from the dike head to the dike body，and the force area gradually increases.