Vertical breakwaters，sea dikes and sea walls are often used in port and costal engineering.The overtopping discharge of a vertical structure needs to be estimated in engineering.So far，the calculating method for the mean overtopping discharge of vertical structures has not been given in Chinese port engineering specifications.So，we summarize several major calculating methods for the mean overtopping discharge of vertical structures.A comparative analysis of mean overtopping discharges estimated by different calculating methods at different water depths and wave parameters are carried out，which can be used as reference for practical harbor engineering design.