Abstract: Dynamic properties of electro-rheological fluids are analyzed. A mathematical model is established by analyzing the designed structure and the working process of the ER shock absorber. In addition, computer simulation was performed to testify the validity of the designed structure. The results reveal that the structure is reasonable and the adjustable damping force under low frequency is feasible. Whereas the adjustability under higher frequencies is undesirable, the paper analyzes the reasons and proposes a valuable suggestion.