Abstract: This paper reported a structural design for point gate plate moulds with four times of mould parting and two times of ejection according to structure characteristics of the shaft sleeve cover cylinder plastic pieces with a ring groove on the inside and lateral convex ribs on the outside, which could realize the automatic injection-molding production. Furthermore, a differential driving inner core-pulling mechanism with an annular groove in the hexahedral T-shaped slot was designed according to the structure characteristics of ring grooves. The relationship between the geometric parameters of mechanism motion was modeled, and the equations for these movement parameters were given. For the convex rib composition on outer ring buckle, a “toggle-type” inclined top mechanism with guide block oriented by T-shaped slots and driven by the push rod was designed. The results indicated that structure of the designed mould was reasonable and the design of the mechanism was simple and reliable.