Abstract: Due to the narrow tuning range and match difficulty of the traditional passive silicone oil damper, a magneto-rheological damping (MRD) was proposed and designed for the semi-active control of sh afting torsion vibration based on the rheological effect of magneto-rheological fluid (MRF). According to the designed MRD structure, a mechanical model was derived and the magnetic field simulation was carried out. After that, introducing the proposed MRD into a crankshaft system, and a coupling model of the MRD-crankshaft system was established. Finally, numerical simulation was carried out based on Newmark method to obtain the torsion vibration response of the crankshaft system. And the influence of the current applying on the MRD on the torsion vibration characteristics was analyzed. The results show that the magnetic flux leakage and magnetic pressure drop outside the plate of MRF are small, and the designed magneti c circuit is effective. Though the traditional silicone oil damper has a better effect on suppressing the 6 harmonic amplitude of the crankshaft, but the effect on suppressing the 4.5 harmonic torsion vibration is not ideal, and the torsion amplitude is increased. Compared with the traditional silicone oil damper, the MRD can make crankshaft system possess obvious characteristics of variable stiffness and variable damping. Supplying a suitable current, the torsion amplitude of the crankshaft system can be minimized over the entire operating speed range.