Abstract: To meet the requirements of the formation of the pinion parts in the rotary disk of crushing machine, a CAE-aided analysis and a UG 3D design method were adopted to design the six-plate die point gate structured mold with one mold and two cavities. To realize the automotive production of injection-molded plastic parts, the mold structure was design by employing a five-point-open-type mold base and a one-half-open slider to perform the automatic demolding of plastic parts. In the case of mechanism design for the half slider, the traditional structure of half slider was modified to set a limiting hook below the half slider to ensure that two side slide blocks in the half slider mechanism could synchronously complete demolding within the plastic pieces of the outer wall on the side of the concave mould. Moreover, to realize the lining plastic helical characteristics on the core self-lubricating rotating demolding, the dynamic model on the side of twice ejection device performed two actions to complete demolding for the plastic parts. This could keep a good turn of the automotive production for injection-molded parts. The mould structure designed by this work is reasonable, and the mechanism is ingenious, which can provide a beneficial reference for the same type of injection molded parts.