Abstract: The basic concepts of wood-based composites are discussed in detail,such as two-phase materials,binders,particles and so on. A new kind of clsssification of wood-based composites is presented.The main principles of composite mechanics are introduced. especially orthotropy,Hooke’s law,strength tensor components,Tsai-Wu failure criterion and combined stress states.Some actual examples of designing wood-based composites are enumerated, such as fiberglass reinforced gluelam,laminated beams, and others.It is the objective of this paper to provide new theories for researches in wood science and development of new kinds of wood-based composites.