Multistage hydraulic cylinders have been used in the place where the length of hydraulic cylinders is limited. Unfortunately,the present multistage hydraulic cylinders can not provide steady thrust in their full travel, as it is usually required by some equipment. In this paper,a digital computer model for a new type of double-stage hydraulic cylinder has been developed and the computing block diagram has also been given.The computing results show that this new cylinder provides a steady thrust during its extension under constant system pressure. The fluid resistant coefficient was found to be an important factor to affect the cylinder working performance and the ratio of the piston areas was found to be a main factor to affect the piston back travel speed and the variation of the cylinder pulling force. A proposal for the election of the factors above has been put forward.