Based on the physical model experiment, this paper studies the wave run-up of the single sloping and composite sloping seawall under the irregular wave action, analyzes the influence of main factors such as wave steepness, slope, wave incident angle, as well as the width and elevation of the platform on the wave run-up, and obtains the calculation formula for the wave run-up of multi-platform seawall and accumulative frequency function. Comparing with the results of more than forty model experiments, this method has a better calculation accuracy, thus may serve as a reference for the engineering design.