The influence of the wavy sea surface on the quality of airborne lidar′s laser beam that transmitted through the wavy sea surface was studied with Monte Carlo method. Simulation results of laser beam energy distribution and the analytical conclusion were presented. In order to obtain the laser beam energy distribution, the classic Monte Carlo model was modified by adding the wavy surface model and the function to calculate the energy distribution of receiver plane. By Monte Carlo simulation, the laser beam energy distributions on certain depth with different sea-surface wind velocities were obtained. From these data, conclusion can be drawn that with the increase of sea surface wind velocity, the laser beam quality decreases, as well as the detection ability of the airborne lidar.