Dike failure is caused by overtopping breakwater,which results in a serious loss of lives and property. To solve this problem,a series of physical model tests were conducted on stable thickness of block revetment on the inner slope of the seawall.According to the erosion of block embankment with different thicknesses,we probe into the relationship between the armor thickness and average overtopping.Equations are given for the stable thickness of facing block on the inner slope. New equations are also presented for average overtopping discharge based on the analysis of mean wave overtopping and comparison of the domestic and foreign existing overtopping formulae. It can provide reference for the design of seawalls.