Recoil resistance of automatic weapon directly affects its firing accuracy. In order to improve recoil mechanism's buffering function of automatic weapon, through analyzing its recoil motion, the design model of magneto-rheological dampers under impact loads was built, and the structure parameters and the control strategy were defined. The dampers' characteristic curve under different magnetic field intensities and different recoil velocities was numerically analyzed and tested on a damper indicator test bench. The test data indicate that magneto-rheological dampers have perfect damping plateau effect and effectively restrain impact loads. The research results provide valuable reference for controlling recoil resistance of automatic weapon.