In view of the permeable sloping breakwaters in the practical engineering, wave transmission characteristics of the sloping breakwater were analyzed without considering the overtopping, by using the combined methods of physical experiments and numerical simulations. The relationship between the wave transmission coefficient of sloping breakwater and multiple wave parameters for breakwater and incident wave were mainly discussed, including the particle size of core material and relative dike width of breakwater body as well as the wave height, wave period, and wave steepness of incident waves. The semi-empirical formulas of wave transmission coefficient under regular wave and irregular wave actions for a sloping breakwater were fitted, respectively. Good agreement between the calculated results and the experiment results was achieved, which demonstrates that the proposed formulas can estimate the wave transmission coefficient of permeable sloping breakwater.