In response to the inadequacy of traditional crankshaft vibration dampers in adapting to system structure and operating conditions, as well as their limited ability to achieve multi-harmonic, wide-frequency vibration control, a novel crankshaft vibration damper featuring controllable magnetorheological（MR）damping characteristics was designed. The damping torque characteristics and adaptive damping control effect of the crankshaft were analyzed and validated. A new disc-type MR grease torsional damper was designed based on theoretical analysis of variable damping torsional control and the structural configuration of traditional silicone oil torsional dampers. Mechanical properties of the MR torsional damper were experimentally tested under various vibration excitation conditions and control currents on a dedicated test platform. A dynamic model for the device based on the tangent hyperbolic model was established. Combined control simulations using AMESim and MATLAB were conducted to compare and analyze the torsional vibration control effects under different scenarios including uninstalled damper, passive control, skyhook control, and fuzzy control during steady-speed and steady-acceleration engine operation. The results indicate that the designed MR torsional damper exhibits variable damping mechanical output characteristics with an adjustable torque range of 4.36, meeting design requirements for variable damping torsional vibration control. The implementation of semi-active control strategy for MR torsional vibration damper can significantly enhance the vibration damping effectiveness of the crankshaft system. Among these, the fuzzy vibration damping control algorithm demonstrates the most comprehensive vibration damping effect, achieving a reduction in torsional angular velocity and angular acceleration by 27.2% to 69.5%. Following closely is the skyhook vibration damping control effect, while the traditional passive vibration damping control exhibits relatively inferior performance.