Abstract: A design scheme of 4-DOF robot for insert milling was proposed, and the 3D structure model of the robot was established. The improved D-H parameters were used to establish the kinematics model of the robot, and the forward and inverse solutions of the robot kinematics were obtained. Based on the kinematics model, the simulation model of the robot is established with the help of Matlab toolbox. Monte Carlo method was used to calculate the reachable space of the robot's end cutter. The robot's trajectory was planned under the conditions of given initial and final positions of the robot, and compared with the profile of the propeller blade surface. The results show that the workspace of the robot terminal cutter is consistent with the surface profile of the large propeller blade, and the trajectory planning is reasonable, which can meet the actual machining requirements.