A combined plastic mold used for compression molding, extrusion molding, injection molding, blow molding, and low foaming molding, mainly comprising a concave mold with a variable cavity composed of a concave mold composite substrate, a concave mold component, and a concave mold composite card board, and a convex mold with a variable core composed of a convex mold composite substrate, a convex mold component, a convex mold composite card board, a cavity cutting component, and a side cutting composite board. Coordinate changes in mold convex, concave, and auxiliary forming systems. Can process series of plastic parts of different shapes and sizes. The plastic processing industry is equipped with plastic molding machines to endow plastic products with complete configurations and precise dimensions of tools. Due to the wide variety of plastic varieties and processing methods, as well as the complex and simple structures of plastic molding machines and plastic products, the types and structures of plastic molds are also diverse.