The invention relates to a rotary pneumatic derusting gun, comprising a gun body shell, at least one steel needle, a steel needle base, a matching base, a sleeve and a gas cylinder; the back end of the steel needle is installed on the steel needle base, and the back end of the sleeve is extended to the inner part through a front shell wall of the gun body shell; the cylinder is installed at the back end of the inner part of the gun body shell; the steel needle base and the matching base are placed in the sleeve, and moved forward and backwards; the back end of the steel needle base is embedded to the front end of the matching base, and the rear end of the matching base is rotationally connected to the piston rod of the cylinder; a rotating mechanism for making the matching base rotate in the sleeve cylinder is further arranged between the matching base and the sleeve cylinder; the rotating mechanism comprises at least one pair of roller beads arranged symmetrically; a groove and an arc chute matched with the roll beads are respectively arranged on the outer circumference of the matching base and the inner circumference of the sleeve cylinder. The rotary pneumatic derusting gun is simple in structure, convenient to operate, and can effectively remove rust spot of an uneven rust face, and has extensive market development and application prospect.