An empirical estimation formula for the maximum water elevation of the impact wave generated by the landslide in a V-shaped river valley is presented. Using the Flow-3D software, a numerical model of the impact wave resulting from the landslide in a V-shaped river valley was established and numerical experiments under 96 conditions were carried out. Effects of the inserting velocity of landslide into water, landslide volume, time of underwater sliding, inserting angle and climbing angle on the maximum water elevation were analyzed respectively. The fitting formula of the maximum water elevation was obtained by regression analysis. The new formula was used to evaluate the maximum water elevation for the Gongjiafang landslide event, and it is shown that the calculated result is very close to the value of the physical experiment.