The work aims to improve the efficiency and safety of metal stretching work, and adapt to people's high requirements for the continuous improvement of tensile products. According to the structure and workflow of the stretcher, the loading and unloading manipulator special for the stretcher with four degrees of freedom was designed. The kinematic relation of the manipulator was constructed in D-H method and calculated. Finally, the structural model of manipulator was established with the Robotics Toolbox in Matlab, and the operating movement state of the manipulator was simulated. Through the simulation of manipulator movement, the posture of each joint and the trajectory of end actuator were obtained. The analysis showed that the three joint velocities and angular velocities were zero at the beginning and end and continuously smooth. According to the simulation results, the movement of the designed manipulator conforms to the actual processing and can smoothly complete the loading and unloading work.