A three-dimensional physical model test of landslide-induced surge was conducted to investigate the characteristics and propagation rules of landslide-induced surge in reservoir. Orthogonal test schemes were designed with varying landslide scale, velocity of landslide into the river, water depth, and river width. The upstream of a hydropower station in the Lancang River was taken as a background. Furthermore, according to the test data, the empirical formula of maximum primary wave height was proposed, and the regression equations of spread wave along the river channel were fitted through multiple regression analysis. Dimensional analysis was adopted as basis and the relative physical variables of classical landslide surge formulas proposed by Pan Jiazheng as reference. According to the proposed formulas, among different instability conditions, the maximum primary surge height induced by Meilishi 4^# was 90.37 m, and the surge height in front of the dam was about 15.09 m. The research results offer reference for the early-warning of landslide surge disaster and the security of the hydroelectric dam.