Abstract: Along with the development of the next generation aircraft, the structural parts appears to more large-scale and macrocosmic, which demanded a higher requirement of the NC machining. However, the cooperation between the designer and the technologist stay in a low level. The designer consider a little of the feasibility for the machining, which brings a lot of difficulties in manufacture. This article research on design for manufacture by means of the knowledge engineering and the typical processing feature study. The research rebuilt the NC machining processing knowledge, formed the design-oriented repository, and summarized the criterion. The research got the balance between the designer and the technologist, which made the design for manufacture and the knowledge digging and reuse became possible. The research on design for manufacture grounded the design and NC machining for next generation aircraft structural parts stable.