Abstract: An multistage adaptive ph-Radau pseudospectra method accord with International Regulations for Preventing Collisions at Sea (COLREGs) is proposed for Unmanned Surface Vehicle (USV) obstacle-avoidance trajectory planning to evade dynamic and static obstacles. The forbidden zones and avoidance waypoints are firstly established abiding by COLREGs, followed by the continuous-time optical model including forbidden zones and maneuverability constraint. The model is next transformed into a multistage trajectory planning model by introducing the interior point. An adaptive ph-Radau pseudospectra for model discretization resolving is then proposed considering solution accuracy and velocity. Simulation experiments finally verified the feasibility and effectiveness of the proposed algorithm.