The invention discloses a collision self-avoiding method and system for an unmanned ship. A given angular speed during collision avoidance is calculated according to the course angle and the sight distance angle of an unmanned ship, so that the course of the unmanned ship is changed to achieve collision avoidance. The system comprises: a tracking control unit used for tracking a known target; a signal acquisition unit used for acquiring the course angle and the sight angle of the unmanned ship; and a collision avoidance control link used for calculating a given angular speed during collision avoidance according to the acquired course angle and sight angle and controlling the course angle of the unmanned ship. According to the collision avoidance method, collision avoidance can be achievedonly by knowing the sight angle without measuring the position and speed information of the obstacle, the defect that a large amount of information of a collision avoidance object needs to be collected in a traditional collision avoidance method is overcome, and the cost can be saved in practical application.