The invention discloses a capping plug injection mould and a capping plug injection moulding method. The capping plug injection mould comprises a lower mould base plate, bearing feet, a bearing plate, a mould core fixed plate, a Haff fixed plate, a small mould core fixed plate and an upper mould base plate from bottom to top. A Haff structure with a thread forming cavity is arranged in the Haff fixed plate and is composed of two pieces of Haff, and a mould core and a small mould core are correspondingly arranged. The mould further comprises a secondary push-off device composed of a first pushing rod fixed plate, a second pushing rod fixed plate, a third pushing rod fixed plate, a pushing rod, a conical pushing rod and a sprue puller, and a swing hook mechanism composed of a swing hook reset plate, a swing hook, a guide rod and a spring is arranged on the secondary push-off device. The injection moulding method comprises mould assembling, injection moulding, cooling, and mould opening ejection. According to the mould opening ejection step, secondary ejection is achieved under matching of the swing hook mechanism. According to the injection mould and the injection moulding method, the mould is simple, demoulding is easy, and injection moulding and mould opening can be achieved without a dedicated injection molding machine.