The work aims to obtain the ergonomic design data of the lower limb rehabilitation behavior of the elderly through the ergonomic simulation evaluation, which provides parameterized support and directional guidance for the optimization of the design of rehabilitation training products. According to existing rehabilitation products, a virtual rehabilitation environment was established and a virtual digital elderly body model was created to define the physical shape and physiological parameters of the elderly. The virtual digital elderly body model was combined with the virtual rehabilitation environment to input rehabilitation tasks and analyze the process of elderly rehabilitation operation tasks. The elderly rehabilitation behavior was subject to the virtual ergonomic simulation. Through the virtual simulation evaluation of the ergonomics of the lower limb rehabilitation system for the elderly, a large number of simulation data were obtained, so that the system's deficiencies and potential risks were found to provide a basis for its improved design. The simulation analysis can help the rehabilitation products to be truly safe, healthy and effective, thereby essentially improving the usability of the rehabilitation training system.