In this paper

taking damping force and its dynamic range as two objective functions

utilizing the programming method of MATLAB

the optimum design of a composite magneto-rheological damper（CMRD）is completed

and the parameter fluctuation is also monitored and analyzed.Based on optimal solutions

the damping force and the adjustment ratio are two conflicting objectives;consequently

they can not be improved simultaneously.The results indicate that the more highly influential parameters of the damping force and its adjustment ratio;The formers are listed in turn:the radius of the piston rod

the length about the axial proud-head of extrusion press

the gap between the cylinder and the piston and the effective length of the piston;The latter successively are:the length of axial proud-head and the effective one about piston

the altitude of this proud-head and the gap itself.And the damping force and its adjustment ratio of CMRD could be concurrently heighten through increasing the piston′s effective length;By means of lengthening the length of axial proud-head

damping force would be increased while then its ratio is decreased.Moreover

the force and its ratio are little impacted by the thickness of the steel bushing.