Combining underwater anti-terrorism needs and ensuring underwater security in designated sea areas, the article describes an acoustic fence equipment for underwater security, which is a cylindrical shape structure anchored to the seabed by means of an anchor system. The underwater acoustic fence warning system is formed by the working arrangement of the network, which is mainly used to detect underwater and water surface threat targets, track and identify them and alarm in real time. It has been successfully applied to the underwater security system of a large-scale sports event water project, and its continuous faultless operation at sea has fully verified its good working reliability.