Anti-ship missile make a fatal threat to naval vessels,medium caliber naval gun plays an important role in aerial defence system of naval vessels,but it has low precision when firing common shells.This paper introduces the operation principle and characteristics of the semi-active laser homing shell and gives out the idea to use the laser homing projectile in the aerial defence of naval vessels.A system scheme is presented,the operation flow chart is also put out.And finally the prospect of the scheme and key technology included are pointed out.