The driving joints of the hydraulic manipulator based on the hydraulic rotary vane actuators (RVA) have many advantages. Aiming for improve the loadbearing ratio of the manipulator, the lightweight design of the RVA joint is carried out. The optimization design mathematical model was established, and the optimization algorithm and penalty function method were analyzed. The parameters of RVA were optimized with the example. The optimized results of the parameters of the swing cylinder with the required torque of 63 kN·m, the number of vanes of 2 and the total system efficiency of 09 were obtained by combining the examples. Through the analysis of the results, the relationship between the required torque and the mass of the RVA, the mass of the RVA and the required torque and the length of the blade, the required torque and multiple optimization objectives were obtained. RVA threedimensional(3D) model was established. The finite element method(FEM) is used to verify the optimization results, which rationality and correctness are confirmed.