Abstract—This paper proposes an equal-distance surrounding control method for second-order nonlinear multi-agent systems (MASs) to encircle multiple moving targets with guaranteed collision avoidance. First, a decentralized estimator is developed to approximate the center of moving targets. Then, an adaptive distributed control law is designed for an MAS to accomplish equal-distance surrounding collaboratively. In particular, conditions for assuring asymptotical stability for the closed-loop MAS are derived. Finally, experimental results with unmanned surface vessels are reported to substrate the effectiveness of the proposed coordinated surrounding control method.