Abstract: To pick up the machined area automatically in numerical control programming, a new methodology for recognizing machining features from a design feature model was presented based on the study about the product modeling method in the design-by-feature systems, product information models (geometric and topological information model, feature relationship model which usually named feature specification tree), the relationships between these two information models, the machining feature class definition in aircraft structure parts, interacting relationships between design features and machining features. By touring the feature specification tree, judging the features- relationships and querying the feature-s surfaces,the feature mapping method from a design-by-feature model constructed the feature attribute adjacency graph (FAAG) and recognized the machining features by matching boundary patterns in the local feature area, then extracted the machined information such as the machined area, the avoided area, the tool approach direction. It can be used to recognize the aircraft wainscots parts.