In this paper, the dynamic performance of the single rod magnetorheological damper (MRD) without accumulator in different working status is researched, which is a new type of MRD developed by us to apply in the environment of explosion and shock. It is concluded that there is no offset force in the new MRD. The maximum damping force and energy absorption capability increase non-linearly with the excitation current and piston’s velocity. The mechanical model of this type MRD is proposed. By comparison of the results of tests with simulation, it is proved that the mechanical model proposed in this paper can simulate the dynamic performance of the new MRD accurately.