The invention discloses a drum-type coating gun which comprises a storage tank and a coating gun body, wherein a rubber plug is arranged at the lower end of the storage tank; an opening is formed in the upper end of the storage tank; a tank cover is arranged inside the opening; a circular cavity is formed inside the tank cover; a first spring is arranged inside the circular cavity; pull rods are fixedly connected with two ends of the first spring; inserting rods are arranged on side walls of the pull rods; the inserting rods penetrate through the circular cavity; a stripy groove is formed in the upper end of the tank cover; the pull rods penetrate through the stripy groove; inserting grooves positioned corresponding to the inserting rods are formed in the inner wall of the opening; the twoinserting rods can be dissociated from the inserting grooves in the side wall of the opening by pulling the two pull rods on the tank cover simultaneously; the tank cover is taken out and is filled with a coating; a first driving motor is arranged at the lower end of the tank cover. The drum-type coating gun is reasonable in structure, reasonable in structural design and simple to operate, a wallsurface can be uniformly coated by a coating, and waste can be avoided.