The invention discloses a combined mold for a plastic extruder. The combined mold comprises a pilot distributor and a forming mold, wherein the pilot distributor comprises a first flow channel, a second flow channel and a third flow channel which are isolated from one another, and the forming mold comprises a first channel, a second channel, a third channel, an extrusion channel and a flow limiting device; the flow limiting device comprises an inner layer cone and a flow limiting cone, and the flow limiting cone which can be adjusted forward and backward is arranged at the front end part of the inner layer cone; the first channel, the second channel and the third channel are isolated from one other, the rear end of the first channel, the rear end of the second channel and the rear end of the third channel converge in the extrusion channel, the first flow channel communicates with the first channel, the second flow channel communicates with the second channel, and the third flow channel communicates with the third channel. According to the combined mold, the pilot distributor is detachably connected with the forming mold in a butt joint mode, raw materials shunted by the pilot distributor can be limited when entering the forming mold, and therefore the raw materials in the forming mold can be uniformly layered, and the thickness of the layer can be adjusted more easily.