Based on 2D simulation survival challenge in International Underwater Robot Contest, puts forward defending strategies based on linear regression for mainstream attack mode. This paper introduced the situation of the competition, and expounded the current mainstream attack and defense strategies. It analyzed the speed of both attack and defensive, and found out the track of the parade to eliminate the speed advantage of the attack side. The results showed that this method can complete the defensive task, the attack fish no longer has the advantage in speed, thus, the defense have a greater possibility to survive. Using this strategy, we once got runner-up in Chinese Underwater Robot Contest in 2015.