This paper summarizes and compares the existing formulas for the wave force reduction of crest walls on vertical breakwaters and rubble mound breakwaters under oblique wave attacks.The paper takes a new rubble mound breakwater of a port in North Africa as an example and compares the calculation results with the results of two-dimensional and three-dimensional physical model tests.The results show that for rubble mound breakwaters under oblique wave attack of 30 degrees，the unit-length reduction coefficient of wave force calculated by van Gent formula fits best with the measured value，and the unit-length wave force reduction formula of each vertical breakwater is conservative in the calculation of crest wall on rubble mound breakwaters.The longitudinal reduction coefficient of total wave force calculated by Mares-Nasarre formula is in good agreement with the measured value，but the difference in reduction effects between horizontal and uplift forces is not considered，and there is still some deviation from the experimental results.The longitudinal reduction formula of the total wave force of the vertical breakwater proposed by LI Yucheng et al.is not applicable to the calculation of the crest wall on rubble mound breakwaters.The research can provide a reference for similar port projects.