To meet the requirement of long-term working operation of Hydraulic Exoskeleton Robot (HER) in use, four new structure reservoirs, based on the analysis of the reservoir heat dissipation theory, are proposed. The heat transfer and flow characteristics of the oil in the reservoir were simulated with calculation by Computational Fluid Dynamics(CFD) numerical simulation method. The structure of reservoir with the best heat dissipation efficiency is obtained, which provides a reference for the optimization design of HER reservoir structure.