The increase in the lifting speed of traditional hydraulic jacks will inevitably lead to the increase in the force required to depress the handle，on the contrary,to reduce the force of the person depressing the handle,that is,to increase the degree of labor saving，will reduce the lifting speed.Aiming at the disadvantage of contradiction between labor saving and speed increasing of traditional hydraulic jacks when lifting objects，a hydraulic system of jack was designed for further labor-saving.In this system,the operation cylinder was changed from the single-acting cylinder of the traditional system to the double-acting cylinder;based on the principle of feedback control,the high-pressure oil from the lifting cylinder as the system output was drained into the rod cavity of the operating cylinder as the system input through the accumulator,the high-pressure oil drained into the rod cavity generated downward hydraulic pressure on the piston of operating cylinder,so the force of the person depressing the handle was reduced.The energy-saving and further labor-saving design scheme of the system was introduced in detail,and the hydraulic control principle of oil circuit was analyzed.The hydraulic system of the designed labor-saving jack can achieve the effect of further labor-saving and energy saving without affecting the lifting speed,and the system tank volume can be reduced at the same time.