Fuzzy neural network (FNN) algorithm was used to model the regulating mechanism of the hydraulic adjustable damper (HAD) and this model was applied to the quarter car test rig.By using the developed model,the damping level of the HAD could be predicted according to the required damping force,piston displacement,piston speed,and temperature of hydraulic oil,thus the required damping force could be obtained by adjusting the stepper motor angle.The results show that the real time damping level of HAD can be accurately predicted by using FNN algorithm.To achieve the practical application of this regulating mechanism,the HAD was mounted on the quarter car test rig to conduct the experiment test,the overall vertical performance of the vehicle was enhanced,which verified the engineering practicability of the developed HAD mechanism model.