A path planning method based on obstacle avoidance workspace is proposed for collisionfree movements of multijoint manipulators. Firstly, computer graphics based on the methods of ray and intersecting points is used to depict the Obstacle Avoiding Planning Workspace (OAPW). Secondly, within the OAPW, a 3rovolutejoint (3R) planar robot manipulator model is created by using the DH coordinates method in MATLAB Robotics Toolbox. Thirdly, performance indicators of the shortest path are used to path planning. Taking into account the contacting interference between the movement of the manipulator and the obstacle, an obstacles expansion method is adopted to the safe distance of the shortest path. Finally, these cases, i.e. the absence and nonabsence of obstacles, and expansion of obstacles, are simulated by applying the forward/inverse kinematics of the manipulator and the interpolation arithmetic.