The damping force generated by the conventional magnetorheological fluid damper is usually related to the driving speed， and thus exhibiting a viscous damping characteristic. In order to obtain a magneto-rheological fluid damper with Coulomb damping characteristics， the large-scale size of a screw-rotary magneto-rheological damper （SR-MRD） is proposed to analyze the mechanical property. Firstly， the structural principle of SR-MRD is analyzed， and the velocity distribution of each fluid channel is calculated based on the Parallel-Plate model. Secondly， a fluid mechanics model of the SR-MRD is established， based on the Herschel-Bulkley model， to calculate the internal pressure drop of SR-MRD and the shear force. Then， the damping torque is calculated according to the fluid mechanics model of SR-MRD， and the effect of key parameters on the damping torque is analyzed. Finally， the performance of an SR-MRD prototype tested by MTS. The research results show that the test damping torque of the SR-MRD prototype is consistent with the theoretical calculation value. In addition， it can not only generate a larger damping torque but also have obvious Coulomb damping characteristics compared with the traditional rotary damper.