Abstract: The composition and characteristic of a Lead Magnetorheological Damper (LMRD) were introduced firstly. Then according to the hysteresis curves obtained from the test of LMRD, a Michaelis-Menten model of an LMRD was proposed, and the parameters in this model were then identified. Finally, the proposed model was verified by comparing the numerical results with the experimental results. The comparison results show that the Michaelis-Menten model can describe the effects of current, displacement amplitude and excitation frequency on mechanical property, and nonlinear hysteresis behavior of the LEMR damper.