The invention aims at providing a welding fixture clamping device. The welding fixture clamping device comprises a strip-shaped mounting block. The bottom of the left side of the mounting block is provided with a mounting groove. A movable block matched with the mounting groove is mounted in the mounting groove. A movable pin shaft transversely penetrates through the movable block. The right end of the movable pin shaft stretches into the mounting block. The left end of the movable pin shaft penetrates out of the mounting block. The bottom of the movable block is connected with a clamping block. The front end and the rear end of the bottom of the clamping block are provided with clamping heads. The right end of the top of the mounting block is provided with a clamping cylinder. According to the welding fixture clamping device, the front clamping head and the rear clamping head are arranged at the bottom end of the clamping block and used for clamping two identical parts; the clamping block is arranged below the movable block, and the movable block is mounted in the mounting groove through the movable pin shaft; in this way, when the mounting block pressed downwards, the movable pin shaft automatically levels the planes of the two parts, and then the parts are clamped; moreover, the device is provided with a positioning block and a limiting groove for positioning. The welding fixture clamping device is uniform in pressure and easy to operate, does not affect welding and can effectively guarantee the quality of assembly parts.