In order to improve automotive passive safety performance, a single rod cylinder magnetorheological damper that applied to the front energyabsorbing structure is proposed and optimized. By means of Bingham plastic nonlinear flow modified model (BPM), taking the maximum damping force and the damping dynamic range as the optimization goals to avoid the design limitation under the high impact condition, the NSGAII algorithm of modeFRONTIER is used to design the structural parameters of magnetorheological damper for multiobjective optimization. Optimization results showed that the maximum damping force and the damping dynamic range are inversely proportional, the optimization algorithm that used made it impossible for two optimization objectives to achieve the optimal at the same time, only to choose the optimized solutions that meet the conditions from all the Pareto solutions, the magnetic field distribution of optimized magnetorheological damper is more concentrated and reasonable.