Abstract: To improve the search efficiency and task coordination of unmanned surface vehicles (USVs) in unknown reef environments, a state-driven cooperative search and response method for multiple USVs is designed in this paper. In the search phase, a dynamically updatable sub-region set is constructed, and adaptive path planning is realized by combining with the Euclidean distance allocation algorithm. In the task execution phase, a dwell-time judgment and degraded scheduling strategy are introduced, and the unification of obstacle avoidance and path control is achieved by integrating the repulsive field model. In the response phase, multi-USV cooperative dynamic encirclement is completed through the target motion prediction, equal-angle encirclement point allocation and radius shrinking mechanism. A 2D simulated sea area with 7 irregular reefs is built on the MATLAB platform, and verification experiments are conducted with 8 USVs. The simulation results show that the proposed method achieves a global search coverage rate of 93%, the average response time of multi-USV cooperative encirclement is 13 seconds after target detection, and both the encirclement success rate and obstacle avoidance rate reach 100%. It demonstrates excellent performance in search coverage effect, response stability and adaptability to complex environments, and provides an effective solution for the cooperative operation of multiple USVs in practical scenarios such as marine patrol.