The invention provides a plastic injection mold for a composite cap overturning bottle cap. The plastic injection mold comprises a mold frame structure assembly, a runner material releasing assembly, a molding assembly, a front mold ejecting out assembly, a thread releasing mechanism assembly and a mold opening sequence control assembly. A gating system is designed into the manner that feeding is carried out from the center of a product through a pin-point gate, and the mod is provided with eight cavities. The ejecting out manner that gas enters from a gas nozzle to carry out gas ejecting is finally adopted. According to the technical scheme, the front mold ejecting out assembly, the thread releasing mechanism, the read mold ejecting mechanism and the improved type mold structure are designed oriented to the problems that in an existing mold technology, an overturning cap sticks to a front die and cannot be completely ejected out in a full-automatic manner in the ejecting out process, manual auxiliary mold releasing is needed, and consequently the mold production efficiency is low; thus, defect-free automatic molding production of the product is achieved, and the product forming quality is effectively ensured; and the plastic injection mold is reasonable in structure design, stable in work, safe and reliable.