The invention discloses a metal plate rapid rounding and welding integrated device. The device comprises a base, wherein a back plate is arranged at the rear end of the base, the device is characterized in that the back plate is fixedly provided with a sizing mold, a lower mold is arranged right below the sizing mold on the base in a up-down movable mode, a left upper mold support and a right upper mold support are arranged on the two sides of the lower mold in parallel, a left upper mold which can move leftwards and rightwards is arranged on the left upper mold support, the right upper mold support is provided with a right upper mold which can move leftwards and rightwards, a mold cavity of the left upper mold, a mold cavity of the right upper mold and a mold cavity of the lower mold arecombined to form a cylindrical mold cavity matched with the sizing mold; and a welding gun support is fixedly arranged behind the back plate, a welding gun is vertically arranged on the welding gun support, the welding gun can move back and forth, and the welding gun is located right above the sizing mold. According to the device, automatic rounding and automatic welding are achieved, the two procedures are continuously operated, the construction period is shortened, the labor and time cost is reduced, and the production efficiency is improved.