Digital composite structures definition is the basis for the data integration of CAD, CAE and CAM for composite structures. The key of digital composite structures definition is the modeling of material structures. In this paper the procedure of material structures modeling and contents of laminate lay-up definition data have been summarized briefly. Today composite structures can not be analyzed with true fiber orientations. True fiber orientations of discrete triangle elements have been used to approximate the final state of ply fibers and a XML file has been used to describe laminate lay-up definition data. Furthermore, automatic mapping of fiber orientation data to the finite element mesh based on user specified tolerances has been used to obtain the automatic data transfer from CAD software to CAE software. Finally, the data integration of the CAD software with two manufacturing systems has been presented.