The invention discloses a double-wall special-shaped wood-plastic water tank extrusion die. The double-wall special-shaped wood-plastic water tank extrusion die comprises a mouth mold plate, a manifold, a supporting plate, a transition plate, a die body 1, a die body 2, a composite mandril, and a plurality of screws; the die body 2 is provided with a feed inlet; the mouth mold plate is provided with a mouth mold hole and a plurality of step-shaped holes; the mouth mold hole comprises a longitudinal groove, a transverse groove, and an arc-shaped groove; the lower end of the arc-shaped groove is provided with a hook-shaped embossment; the lower end of the longitudinal groove is provided with a concave arc-shaped groove; the composite mandril comprises a plurality of small mandrils, is inserted into the mouth mold hole, and is arranged on the supporting plate via imbedding feet in a segmental manner; and the screws are used for connecting the mouth mold plate, the manifold, the supporting plate, the transition plate, the die body 1, and the die body 2 successively. The double-wall special-shaped wood-plastic water tank extrusion die is novel in structure; assembling and disassembling of the mandril are convenient to realize; the shape of processed wood-plastic water tanks is composite; material consumption is low; strength and rigidity are high; and appearance is beautiful.