Abstract: The paper introduced the theory and the structure of the magneto-rheological (MR) absorber, based on the parallel plate flow model and Bingham model, a mathematic model of the damper force was presented as the basic theory for the structure design of the damper. By way of the bench test for the MR damper, the damping-displacement and speed characteristics were studied. And based on the skyhook on-off control algorithm, the real car test platform was built for the road test. The experiment data indicats that: compared with the traditional passive suspension, the MR semi-active suspension can restrain the low frequency resonance amplitude significantly and reduce the acceleration RMS of vehicle body; the MR absorber can improve the vehicle ride comfort effectively.