A series of flume experiments are conducted to study the influence of the seaward-side slope of a levee on the discharge of combined wave and surge overtopping under extreme sea conditions. By comparing the discharges under different seaward-side slopes，this paper analyzes the influence of the seaward-side slope on the discharge of combined wave and surge overtopping. The following conclusions can be drawn from the study：1）In the range of -0.6＜Rc/Hm0＜0，the discharge of combined wave and surge overtopping is significantly affected by the seaward-side slope of the levee. 2）Within this range，when the seaward-side slope of the levee changes from 1∶1.5 to 1∶4.25，the discharge of combined wave and surge overtopping under the same wave condition first decreases and then increases slightly. With the experimental results as a basis，an empirical formula for the discharge of combined wave and surge overtopping considering the seaward-side slope of a levee is proposed to provide a reference for the safety assessment and protection of levees under extreme conditions.