The invention discloses a self-collision monitoring system for a humanoid robot and a monitoring method thereof, and relates to the field of robot control. In order to improve the accuracy of collision detection of a robot and protect the safety of the humanoid robot in real time, a collision model, a discrete adaptive window angle speed calculation method and a GJK algorithm are built by using a ball scanning convex body; a rapid high-precision collision detection monitoring system which is independent on task planning and control of the robot is developed. The system runs in a cycle, a joint angle of the robot is taken as an input, whether the robot collides or not is judged, a sudden stop instruction is transmitted to a robot controller in collision, and the system does not affect operation of the robot when the robot safely runs. The self-collision monitoring system is applicable to robot control.