The structure of pier-column permeable wharf is often exposed to complex forces under the action of waves. For rectangular caisson piers，the current domestic port engineering codes only analyze the total horizontal force of a single caisson under the action of forward and 45° oblique waves. There are neither calculation methods for the attenuation law of wave forces in pier groups，nor related results in existing studies. Taking a bulk cargo terminal project with gravity caissons in Maoming as an example，we carry out three-dimensional physical model experiments to study the wave height distribution around rectangular caisson piers and attenuation laws along the way，and analyze the horizontal，the lateral and the uplift forces and the overturning moment，as well as the attenuation law of wave force along the way of representative caisson piers. The results show that the wave height attenuation amplitude is the largest within the 5 caisson piers firstly exposed to the waves. The attenuation amplitude of the wave force on different caissons along the way shows the same trend as the wave height attenuation. The calculation method for the coefficient of cylindrical pier group in the code is not suitable for the rectangular caisson pier group.