This paper summarizes and compares the existing calculation methods for the average overtopping volume of mound breakwaters under oblique wave attack both at home and abroad. Taking a new mound breakwater of a port in North Africa as an example，we calculate the average overtopping volume and compare it with the result of a 3D physical model test. The results show that when the wave attack angle ranges from 0° to 20°，the reduction effect of oblique waves on the average overtopping volume is insignificant，and they can be considered perpendicular waves in design；when the wave attack angle is greater than 20°，the reduction effect is gradually significant，which should be taken into account. For AccropodeTM armored mound breakwaters with a wave attack angle of 30°，the calculation results of the neural network method and van Gent formula（Combination 2）are close to those of the physical model test，and the results of the Galland formula，van der Meer formula，and van Gent formula（Combination 1）are similar and relatively small. The calculation results by Chinese standards are conservative；the Lykke formula is risky，and thus it is not recommended.