Discharge is one of the most important parameters in the design of dikes, with the increasing of sea water elevation due to the climate changes, the risk of dike damage caused by combined wave and surge overtopping is increased. For safety reason, it is necessary to understand the discharge of combined wave and surge overtopping as it may cause serious damage to dikes. However, previous studies usually neglect the effects of dike structural parameters such as seaward slope gradient on the discharge of combined wave and surge overtopping. To this end, series of physical experiments are carried out to study the effects of structural parameters on the discharge of combined wave and surge overtopping under various wave conditions. It is found that the difference in wave passing patterns caused by the seaward slope gradient is an important reason for variation of combined wave and surge overtopping discharge. According to its unique characteristics, the semi-empirical equation of average discharge of combined wave and overtopping is obtained by curve fitting of the laboratory measured data.