In the control of traditional hydraulic systems，ordinary hydraulic cylinders generate large pressure fluctuations in the condition of varying load．For this case，we design a fourchamber hydraulic cylinder．By using the hollow rod as another cylinder body，we make twochamber ordinary hydraulic cylinder into fourchamber．In the control of digital fluid power systems，further increase in the number of force values can be obtained by increasing the number of supply pressure to adjust to the varying load．The results show that the fourchamber hydraulic cylinder can save spaces and costs, improve the working efficiency and effectiveness as well．