In this paper, the structural feature and forming technology of two automobile engine covers are analyzed. The mould structure with two cavities is designed and the working process of the injection mould is discussed. The mould structure is complicated. Ten core-pulling mechanisms are designed reasonably in one mould and demoulding of the plastic parts is realized. Many inserts and standard parts are used in the injection mould, so the economical efficiency of the injection mould is well and the injection mould can be maintained conveniently. The injection mould is already in mass production. Industrial practice proves that the action of the core-pulling mechanisms, ejector mechanisms and resetting mechanisms is stable and reliable. The plastic parts produced can meet the customers' technical requirements.