It is one of key technologies of improving its production cycle and achieving design, product and inspection closed chain Inspection and planning technology of aerospace sheet metal parts. Expert system of inspection and planning technology for aerospace sheet metal parts is researched in this article on the basis of case-based reasoning. It focuses on the typical aircraft sheet metal parts. Knowledge of aerospace sheet metal parts inspection is divided into plate knowledge and its case library, section knowledge and its case library, skin knowledge and its case library, panel knowledge and its case library. Case feature attributes are expressed in production rules, reasoned and recognition based rules and then modifying case and getting inspection card of aircraft sheet metal part.