In order to optimize the connectivity of underwater acoustic sensor networks(UASNs) and to improve the robustness and adaptability of the network topology based on double-autonomous underwater vehicles(AUVs), a topology optimization mechanism of UASNs is formulated by taking the advantage of the topology optimization idea. After the inherent law of UASNs topology formation being found, the method for optimizing network topology is proposed, which eliminates those key nodes by using the triangle principle and can improve the survivability of network regeneration. The simulation results show that the mechanism can improve survivability of the network effectively about 50{\%} with the network coverage loss 8.5{\%}.