The utility model relates to a supplementary clamping device for processing of metal tubular product. Include that the bottom has the backup pad of bottom plate, at the articulated mounting panel that is connected with in its top, still include the articulated cylinder of connecting at mounting panel rear side middle part of cylinder body, at the articulated support arm that is connected with of piston rod of the cylinder's tip, have an otic placode at the inboard middle part rigid coupling of support arm, articulated connection at the top of mounting panel rear side of tip of otic placode, seted up constant head tank and first jack on the terminal surface of support arm, include still that the rear portion has the last clamp splice of locating piece and first inserted bar, bottom seting up the draw -in groove, the locating piece is located the constant head tank, first inserted bar is located first jack, being equipped with the breach of rectangle in the front portion at mounting panel top, offering the middle part of spout, diapire at the middle part of the back lateral wall of breach and offered the second jack, the length direction of spout is on a parallel with the axial direction of second jack, includes still that the bottom has a lower clamp splice that the draw -in groove was offered to second inserted bar, top, thereafter the position in the spout, the second inserted bar lies in the second jack.