The computer-aided aircraft design is mainly realized in aircraft manufacturing enterprises, but the aircraft product tolerance design still depends on calculation by hand. A method to construct a national standard tolerance, fitting and aircraft construction tolerance database by using VC++ and Access is put forward in order to realize automatic lookup of tolerance and fitting. With the help of this automatic lookup program, engineers can design or verify tolerances conveniently, quickly and precisely. This method provides a basic technique to realize the computerization of aircraft constructuion tolerance design.