Dynamic response is extremely important for Magneto-rheological (MR) damper, and directly affects the MR damper performance in semi-active control system. The dynamic responses for driver, damper and the whole controlled system are discerned, and the research contents and directions of dynamic response of MR dampers are also indicated. Based on the operation characteristics of MR dampers for automotive suspension, a reasonable description of dynamic response is proposed, and some important issues for dynamic response testing are discussed. Finally, the influence factors upon the response time of the MR dampers are investigated, and the directions for further improvement are given.