Abstract: Based on the finite element analysis of magnetic field, taking damping force and its adjustment ratio as two objective functions, utilizing multi-objective genetic algorithm (MOGA), the optimum design of MRF damper was completed. Based on optimal solutions, the response surface and linear correlation coefficient matrix were analyzed. The results indicate that, the most highly influential factors of the damping force and its adjustable ratio are as follows: the gap between the cylinder and the piston, the ratio between the effective length of the piston and the gap, the effective area of the piston. The gap between the cylinder and the piston and the ratio between the effective length of the piston and the gap itself have the greatest influence on the damping force and the force’s adjustment ratio respectively. The results also show that the damping force and the adjustment ratio are two conflicting objectives; consequently, they can not be improved simultaneously. Moreover, with a specific restriction for the factor of the damping force, the effective length of the piston has an optimal value.