A novel rotary magnetorheological damper for tremor suppression robot is presented. Base on properties of magnetorheological fluid and magnetic core material, the magnetic circuit design method suitable for the structure of the damper was worked out, the magnetic circuit was designed used the design method, the mechanical and the electric parameters of the damper were calculated. Depending on mechanical structure characteristics, built the 3D model of the damper with the ANSYS APDL, after completed magnetic solution, magnetic field quantities and mechanics performance parameters of the damper were got. With the results of the magnetic analysis and the constitutive relations, the performance prediction of the damper was realized. Then the magnetorheological damper and the mechanical performance test system were developed, the mechanical performance of the damper was researched used the test system, the damper’s properties: torque vs rev and yield torque vs current were obtained, and these results was analysed, these experimental results show that the mechanical performance of the magnetorheological damper is similar with the expectation.