Based on the previous research on wave forces of perforated caisson，we further study wave forces at the forefront of the perforated caisson with permeable superstructure through physical model tests of irregular waves.Analyzing the regular pattern of pressure distribution and comparing it with the existing formula of wave pressure,we find that the formula can be modified based on the Aida Yoshizane formula which is applied to the calculation of the pressure distribution of the upper structure’s panel and the forefront of the lower part of perforated caisson with permeable superstructure.The stringers of the upper structure suffer greater relative point pressure.So,the relative wave pressure of stringers is studied separately and the empirical formula for calculating relative wave pressure is provided here.