In order to acquire the optimal purpose in ship counterwork, research the optimal end variable-trajectory tactic of anti-ship missile. Firstly, the model is built for anti-missile defense system of warship, and has researched the attack-defense countermine course of anti-ship missile and ship-air missile. Based on this, the terminal maneuver method of anti-ship missile is given. At last, the penetration tactic of the optimal terminal maneuver is conclude according to the principle of minimal ship-air missile’s average miss distance. The experiment shows that the best penetration effect can be got with the tactic.