The chaotic motion of composite beam with initial defect under moist and thermal state was studied considering the influence of shear deformation. And the factors that affect the chaotic motive region, such as shear deformation, initial defect, as well as temperature and humidity were discussed. The following conclusions were obtained:（１）the chaotic motive region of composite beam with initial defect increases when temperature ascends, or when the extent of the initial defect descends, or when the amount of the humidity rises, or when the influence of shear deformation is taken into account;(2)the chaotic motive region of composite beam without initial defect is larger than that with initial defect under moist and thermal state.