The working principle, valve system features and hydraulic fluid mechanics theory of unidirectional flow hydraulic damper were analyzed. With the high-speed train KONI lateral damper as example, according to its structure and parameters damper hydraulic control model was established in the environment of Easy5. Maxwell co-simulation model of damper was established by using Easy5 and ADAMS co-simulation interface technology and taking joint stiffness of the damper into consideration. Damper performance simulation and test results were compared and analyzed. The results show that the model established in is accurate and reliable.