The utility model provides a three-layer co-extrusion foaming reinforced plastic building template. The three-layer co-extrusion foaming reinforced plastic building template comprises an upper hard surface layer, a lower hard surface layer and an intermediate foaming core layer, wherein the upper hard surface layer and the lower hard surface layer are made of PVC (Poly Vinyl Chloride) plastics; the foaming core layer is formed by foaming thermoplastic resin; and the foaming core layer is thicker than the upper hard surface layer and the lower hard surface layer. The three-layer co-extrusion foaming reinforced plastic building template is an energy-saving and environment-friendly product, and has the advantages of long life cycle, recyclable performance, conservation in wood resource, smooth surface, good effect on demoulding, water resistance, moisture resistance, and high processibility of the product.