The invention relates to a rear portal frame structure of an enameling machine. The rear portal frame structure comprises a body and a portal frame. The portal frame is arranged at an outlet of the body, a plurality of groups of guide rolls and a face plate are arranged on the portal frame, and the face plate is netted and hollow-out. The rear portal frame structure has the advantages that the traditional platy closed face plate is modified to form a steel wire mesh braided by stainless steel, so that falling enameled wires can be stopped, and the rear portal frame structure is good in ventilating and cooling effect, low in cost and convenient to replace.