The utility model provides a pneumatic type toy gun with a movable type cartridge. The pneumatic type toy gun comprises a gun body, a cartridge, a transmitting mechanism and a trigger mechanism, wherein a circular connector arranged at the front part of the gun body is connected with an externally built cartridge; a bullet filling device is in a tubular three-way structure, a bullet inlet hole is arranged at the upper part of the bullet filling device, and the inner wall surface at the front part is formed into a unidirectional circular ring; a gas room comprises a head and a chamber. The pneumatic type toy gun further comprises a cartridge holder which is clamped at the front part of the casing of the gun body so as to clamp rod-shaped bullets. The pneumatic type toy gun provided by the utility model is a novel toy through which two kinds of bullets can be mounted and transmitted, the externally built cartridge can be changed conveniently, which is favorable for keeping complete bullets, the bullets can be continuously reloaded and fired, and the pneumatic type toy gun is strong in amusement. The cartridge holder device outside the gun body provides a mode through which the bullets are taken and carried conveniently, and the pneumatic type toy gun is simple in structure and good in practicability.