Aiming at the difficulty of using accurate analytical formulas to represent the Tripod parallel robot workspace boundary surfaces, a method called surface-sweep analysis combined with the shape of mechanical structure analysis was proposed to give an accurate expression to the workspace of Tripod parallel manipulator. On account of the Tripod parallel robot, the geometric model of the parallel robot was set up and the architecture of the parallel robot and the driving mode of the parallel robot were introduced. Based on the algorithm of forward and inverse kinematics solution, the scope of sweeping space and envelope surface expression of this sweeping space considering one of the robot parallel’s open chains were obtained. Then, the six envelope surfaces were drawn in sequence and the overlap part of the six sweeping space was solved. In 3-D software, the public workspace can be obtained by using boolean operation algorithm. Then, under the consideration of mechanical structure of shape analysis and physical constraints, the actual workspace and boundary surface expression of robot can be obtained. Furthermore, the singularity of the obtained workspace was analyzed. According to the comparison of workspace measured by the three coordinate measuring instrument and the workspace obtained by 3-D software, the validity of this analytic method was verified by using the error analysis method, which layed foundation for the next step to figure out the influence of mechanical parameters on the workspace and do some work on the size optimization of the parallel robot.