Aiming at the local defect repair of the inner wall of hydraulic support cylinder in mining,a welding manipulator which could go deep into the hydraulic support cylinder for inner wall repair was designed.Based on the improved D-H parameter modeling method,the kinematics model of the designed inner surface repair welding manipulator was established,and the forward and inverse kinematics of welding manipulator were analyzed and solved.With the help of MATLAB software and Monte Carlo method,the effective workspace of the welding manipulator was simulated and analyzed.Robotics Toolbox was used to plan the joint trajectory of the welding manipulator,and the angular displacement,angular velocity and angular acceleration curves of each joint were obtained by simulation.The simulation results show that the designed welding manipulator runs smoothly and the trajectory is continuous,which meets the kinematic requirements.