Based on the systems engineering theory, this paper reviews the trend of researches and developments on vehicle semiactive suspension systems, analyzes states of researches on electrorheological fluids and magnetorheological fluids material,and puts forward semi_active suspension sytems based on magnetorheological fluids damper. On the basis of summing up existing methods for vibration control on semi_active suspension systems, emphases are put on the discussion of aplication of PID control. linear optimal control,adaptive control and intelligent control on the semi_active suspension systems. The compound control strategy is put forward based on the skyhook damping control theory, fuzzy control theory and adaptive control theory. Moreover, the integral idea about the research and development of semi_active suspension is based on MR damper,and discusses some theories and applied problems deserving research.