Collaborative robot is a kind of robot designed to interact closely with humans in the co-working space. With its safety, flexibility, high speed, portability and other characteristics, it gradually infiltrates various fields, such as assembly production line, household labor service, health insurance field and logistics industry. The joint module of Hangzhou Zhizheng Collaborative robot uses a servomotor with a hollow structure without a frame, and the cable passes through the inside of the medium rotor, reducing the overall weight and size of the robot, improving the overall appearance of the robot, while providing engineers with the high performance, long life and easy installation they need.