Abstract: The magnetorheological damper is a kind of intelligent semi-active vibration damping device with good prospects，but the current magnetorheological dampers mostly use shear valves as the working mode． The vibration damping effect of this type of damper is poor when used in hydraulic mechanical legs，press leveling and other areas due to the insufficient output force caused by the size of the structure． In this paper，a shear-extrusion hybrid mode magnetorheological damper was designed to solve the problem，and a full-channel magnetic circuit structure was used to replace the traditional magnetic circuit structure to increase the maximum output and dynamic range． This research carried out the structure design and principle analysis of the new magnetorheological damper，established the mechanical model，simulated the magnetic field，and made optimization on the structure． The superiority of the new magnetorheological damper was proved by the prototype test． The above tests and simulations show that the damping force of the new magnetorheological damper can be up to 1065N in the shear valve type and 4939N in the squeeze type． Especially，when the piston coil is fed with reverse current，the magnetic induction intensity of the new damper in the piston damping channel is all above 0. 2 T，while the magnetic induction intensity of the traditional damper only nearly 40% reaches 0. 2 T． When set the current in the same direction，the magnetic induction intensity of the new damper more than 80% can reaches 0. 3T，while the damping channel of the traditional damper only nearly 40% reach 0. 3T． Compared with the traditional magnetorheological damper，the shear-extrusion hybrid mode magnetorheological damper has a larger output value and a higher dynamic adjustable coefficient．

Key words: magnetorheological fluids, shear flow, extrusion, vibration control, structural optimization