Abstract: Implementing digital composite structure definition is the base of achieving the data integration of design, analysis and manufacture for aircraft composite structures. The digital composite structure definition consists of the modeling of geometry and the modeling of material structure. The process of material structure modeling and data contents of laminate lay-up definition were summarized. The fact that today the composite structures can not be analyzed based on the final shape with true fiber orientations was put forward. True fiber orientations of discrete triangle elements were used to approximate the final state of ply fibers and XML(extensive markup language) file was used to describe laminate lay-up definition data. Using automatic mapping of fiber orientation data to the finite element mesh to obtain the automatic data transfer from design to analysis was discussed. At last, the data integration of design with cutting system and laser projection system and the organization of interface data were studied.