Objective A 2-PSU/ RR parallel ankle rehabilitation robot was designed, and the biomechanical properties of human muscles were also analyzed, so as to study rehabilitation strategy of the ankle rehabilitation robot. Methods The actual workspace of the robot was obtained by numerical discrete search method, and the effect of structural parameter changes on the height of robot moving platform was explored. Then the human biomechanical responses such as muscle force and muscle mobility were obtained by human biomechanical simulation software AnyBody, so as to investigate the effect of moving platform height changes on muscle behavior. Results The robot could meet the demand of ankle plantarflexion/ dorsiflexion and inversion/ eversion motion. Appropriately increasing the initial inclination angle and decreasing the length of the fixed-length bar enabled the ankle rehabilitation robot to have a lower overall height. The height of the moving platform was decreased by 10 mm in turn, and the muscle force and muscle activity of the human body involved in the movement were decreased to a certain extent. Conclusions This study provides a new design solution for ankle rehabilitation, offers theoretical guidance for motion analysis of the ankle rehabilitation robot, and accelerates rehabilitation of the patients’ ankles by modifying the mechanism parameters.