Abstract: The background of developing two-stage and three-stage gas guns driven by compressed nitrogen is discussed, and the design technologies as well as their performances are analyzed. The effects of the mass of piston and the mass of projectile on the velocity of the projectile are analyzed, and the effects of the chamber pressure and the pressure of the pump tube on the velocity of the projectile are discussed. An experimental study of two-stage and three-stage gas guns is carried out. The future developing prospect of multi-stage gas guns driven by compressed nitrogen is assessed.