The kinematics model of the robot was established, and its structural parameters were studied. Based on coordinate transformation, the inverse solution of the robot was obtained. Its workspace was solved by MATLAB program. Three-dimensional diagram and projection drawing on XY plane of workspace were obtained. In addition, the sorting range various with the different value of Z was studied and obtained. Finally, on the premise of meeting working range of the robot, using the minimum mass of the moving parts as optimization objective, the structural parameters of the sorting robot were optimized using the search method. Simulation results show that the optimized robot can achieve the minimum weight of moving parts and meet the preset sorting range. It is also ensured the sorting flexibility.