If there has berm build on the surface of the step style dike then the height of wave runup will decrease significantly due to the weir effect of water flow over the berm. By using the theory of conservation of mass, the decrease rate of the height of wave runup can be calculate. The empirical equations that proposed by van der Meer etc. (1992) is quoted to calculate the height of wave runup also and use it to compare with the measuring data which obtained from the experiment in this study. The correlation between the relative height of wave runup and the surf similarity parameter in various berm widths shows the weir effect of the berm has significant in decrease the height of wave runup. It indicate the more the berm width increase the more the wave runup decrease. Yet, when the width of the berm increase up to 7 cm then the decrease rate of the height of wave runup becomes very small.