Abstract: This paper presents an approach to the construction of the knowledge base of mechanical parts from three-view engineering drawings. The philosophy of this method is to treat a mechanical part as consisting of various elementary objects while an engineering drawing as consisting of a number of loops. We can find all the elementary objects which a mechanical part is considered to be composed of through matching the loops in different views, and then represent the parts in terms of frame knowledge representation and store them in the knowledge base of mechanical parts.