In order to describe the behaviors of hydraulic damper with single tube on mountain agricultural tractor, the physical model of the damper was built based on fluid dynamics. Both of the velocity behavior and displacement behavior were obtained. The simulation diaphragm conformed well with the test results. The discussion about influences of the key parameters on performance was presented. The conclusion is that valve diameter, velocity and air pressure are crucial to the damper. Hydraulic damper with single tube can adapt to high vibration velocity, which is suitable for mountain agricultural tractor.