Abstract: Aimed at the demolding difficulties with three characteristics of plastic parts in automatic injection molding of shell plastic parts, a two-plate mould was designed. Banana gate was used to pour the mold. The die is divided into two parts, in which one is for the core pulling drive of the first core pulling mechanism of the front die and the other is for the opening of the cavity of the plastic part and the simultaneous completion of the side core pulling demolding of the reverse buckling of the outer wall of the plastic part. In order to realize the core-pulling function of the front-die core-pulling mechanism, a cylinder-driven top-plate mechanism was installed on the side of the fixed-die frame, which was used to drive the bending pin of the front-die inner-wall inverting front-die bending pin to drive the inner core-pulling slider in the cavity to realize the core-pulling-out and demolding of the inner-wall inverting of the plastic part. The slider of the outer-wall inverting of the plastic part is driven by the oblique guide pillar to implement the side. For core-pulling demolding, inclined hole is driven by cylinder core-pulling inclined core to demold. The layout of die structure is reasonable, and the mechanism design is ingenious. Such a design provides a good engineering reference for the mold design.