Abstract: Mold parting direction is an important factor to verify the moldability of a molded part and its determination is the first step to achieve automatic design of injection mold or casting die．Amethod using automatic feature recognition is proposed in this paper to determine the parting direction．First，the features used in the injection mold are classified，the candidate and possible parting directions of every class of feature are established．Then，all the features in the molded part are recognized by a universal hint-based feature recognition algorithm．The candidate parting directions of the recognized features are automatically determined in different groups．The optimal parting direction is finally determined using the new criteria proposed in the paper．From case studies on several industrial parts，the methodology developed is found to be efficient in determining the optimal parting directions of injection molded parts．