In the vehicle ride comfort experiment,due to the high cost and difficulty in ensuring reliability of existing adjustable damping dampers,the method of′replacing different passive dampers′ is usually used to test the impact of the damping.However,this method has a long experiment cycle,the efficiency is low,and the connecting parts of dampers are easy to be damaged.Thus,an adjustable damping hydraulic damper was developed.The damping adjustment was realized by regulating the orifice area through the relative rotation of the core rod and the piston rod driven by a stepping motor.An analytical design method for adjustable damping hydraulic dampers based on the optimal damping ratio of vehicle suspension systems was proposed.The speed characteristic curve,the damping adjustable region and valve system parameters of adjustable damping hydraulic dampers were designed,and the functional relationship among the damping ratio,the adjustable flow hole area and stepper motor angle was established.Then,a prototype was built and a performance test was carried out.The results show that the relative deviations of the damper forces between the experimental values and the required are less than 2.0%,the fatigue life meets the experimental standard requirements by more than 2.1 times,indicating that the damper meets the performance and reliability requirements,the effectiveness of the proposed analytical design method is demonstrated.This damper can effectively improve the efficiency of vehicle smoothness experiments and avoid damage to the connecting components of dampers.It can also be widely applied to vibration reduction characteristic experiments and vehicle semi-active suspension experiments.