Abstract: The invention herein relates to a hydraulic oil cylinder structure with reverse force function comprises of a piston rod with one threaded end and ring base on the other end; the piston rod is housed in order with a elastic cushion, a cover body, a cushioning circle, a spring, a spring fastening member, a tension spring, a cushioning ring and a piston; when the piston rod is stepped downwards for physical exercise, the piston rod can resume automatically by the reverse force function of the tension spring to allow the exerciser to choose to operate by exercising with single foot, both feet up or both feet down.