The invention discloses a tool following plate structure on an air conditioner pipe valve welding device. The tool following plate structure comprises a bottom plate. A water groove is fixed to one side of the bottom plate, and a protrusion is formed on one side wall of the water groove. A water discharging hole is formed in the front side wall of the protrusion, and a water blocking ball abuts against the water discharging hole. A guide rod is formed on the water blocking ball, and a compression spring is inserted in the guide rod in a sleeving manner. The two ends of the compression spring abut against the inner wall of the protrusion and the water blocking ball correspondingly. The guide rod penetrates the rear side wall of the protrusion, and a connecting rod is formed on the guide rod. One side of the connecting rod is connected in a guide groove formed in the outer side wall of the water groove in an inserted manner, and a rack is formed on the part, in the guide groove, of the connecting rod. The rack is engaged with a gear ring, and the gear ring is formed on an arc part at one end of a rotating rod. The arc part is hinged to a support through a hinge shaft, and an arc electromagnet is fixed to the support. The rotating rod is attracted to the electrified electromagnet in parallel to the rack. By means of the tool following plate structure, an independent water discharging structure is additionally arranged, and therefore a tool following plate or a conveying chain belt on the outer side of the water groove can be prevented from being rusted.