Because of their simple structure, rapid response, large force, low power requirements and robustness, magnetorheological fluid (MRF) dampers have shown to be one kind of hopeful semi-active control devices in the field of anti-vibration of civil engineering structures. In this paper, the key parameters such as structural parameters, magnet coil, original inner fluid pressure and their influence effect on performance of shear-valve MRF damper was discussed. Results show that, the diameter of cylinder and gap between piston and cylinder is the main structural parameter that influence amount of damping force of MRF damper, parallel and inverse connection of magnet coils are apt to improve damping force and response time. Results also show that proper initial inner fluid pressure is propitious to reduce lag of response time or damping force at reverse moving of piston.