For rock mound breakwater design, Van der Meer formula is widely used by international codes for amour rock stabilized mass calculation. For the notional permeability coefficient Pvalue in the formula, four standard configurations are defined based on differences on core, filter layer and amour layer, the notional coefficients are recommended to be P =0.1, P =0.4, P =0.5 and P =0.6.In engineering practice, mound breakwater is not accord with standard of any kind of situation, often characterized by two standard situation in the middle of the form, especially for structure which has an impermeable core with filter layer and geo-textile. This paper introduces Van deer Meer’s study for notional permeability coefficient and the study progress in recent years, and the research results are taken into engineering practice. It may provide some reference for overseas engineering design.