The torsional damper of dual mass flywheel (DMF) should be different under different conditions of ve- hicles.Aiming at the above issue,the MRF is applied to the DMF by taking into account the rheological behavior of the magneto- rheological fluid (MRF) in a magnetic field.Then,by designing a two- stage stiffness curve,arc spring parameters,magnetic circuits and a damping torque in working clearance,a magneto- rheological- fluid dual mass flywheel (MRF- DMF) controlling the torsional damper through the exciting coil current is designed and made,and its service performance is verified by a static characteristic test.Finally,an AMESim model is constructed and verified by a bench test.The results indicate that the semi- active control of the torsional damper of MRF- DMF can be realized by adjusting the exciting coil current.