Abstract: The early stage of product development has a crucial effect on capabil ity, cost and quality of products. Research on theory and approach of early proc ess planning was based on feature information, and could not utilize rough-gra n ularity incomplete product information. Therefore, core process skeleton based p rocess planning approach was proposed on the basis of key characteristics which have been proposed to express rough-granularity incomplete product information. Core process planning is a kind of abstract of process plans which satisfy key characteristics requirement, and it expresses core process of various variation of product/part family. Process plans can be configured rapidly according to e mbranchment and existence rules. The procedure of process planning on the basis of core process skeleton includes four steps: determining product/part family, s earching core process skeleton, configuring core process and process route plann ing. Validity rule, principle rule and customized rule were employed to assure v eracity of process planning. Finally, machining process of the girder of the win g was used to validate feasibility of this approach.