The utility model discloses a clamping tool for hardware, and relates to the technical field of clamps. The device comprises a base, and a first clamping assembly is fixed to the upper surface of thebase through four fixing stand columns; two cylindrical guide rails are fixed to the upper surface of the base through fixing rectangular blocks. Two cylindrical sliding blocks are in sliding fit withthe two cylindrical guide rails respectively; a second clamping assembly is fixed to the upper surfaces of the four cylindrical sliding blocks. The lower surface of the second clamping assembly is connected with the base through an electric lead screw sliding block. The first clamping assembly comprises an L-shaped plate folding piece. A first double-rod air cylinder is fixed to one surface of the first clamping assembly. A second double-rod air cylinder and a third double-rod air cylinder are fixed to the adjacent surfaces of the first clamping assembly correspondingly. According to the utility model, the first clamping assembly and the second clamping assembly are designed for collinear clamping arrangement of two hardware to be welded respectively, and the welding end is tensioned by the electric screw rod slide block for straight welding, so that the problem of non-straight welding of a square tube or angle iron is solved.