Preliminary bubble distribution model of ship wake is presented according to the law of bubbles density varying with time and depth,and bubble motion. The laser backscattering properties of air bubbles of the ship wakes under I,IA,IB-type seawater are numerically simulated with the multilayer Monte Carlo method and Mie scattering theory. Different results under 20 m and 30 m depth with the effect of phytoplankton are analyzed. Simulation result shows the light backscattering of ship wakes is increased along the ship stern from far to center;and the backscattering is influenced by phytoplankton in ocean obviously. Results show that the laser backscattering of bubbles of the ship wakes can be used as a fuse of torpedo.