Abstract: Rotor blade is the core power structure of advanced helicopter, which is often unbalanced or invalid due to excessive vibration during high-speed rotation, which seriously affects the flight safety of helicopter. Because of its excellent mechanical properties, composite materials are widely used in the research of the rotor blades. Therefore, accurately predicting the vibration characteristics of composite blades has great significance on the overall design and daily maintenance of advanced helicopters. The coupling relationship between the mid-surface shear strain and other mid-surface strain, curvature and shear flow caused by material anisotropy of the thin shell is considered. The simplified blade is the thin-walled closed-section composite beams (TWCSCBs). The Lagrange principle and the assumed mode method are used to derive the dynamic equation of the rotating thin-walled composite beam. The rationality and accuracy of the dynamic model are verified by comparison with the results of finite element simulation and literature. On this basis, the influence mechanism of the coupled deformation terms and shear flow in mid-surface shear strain caused by material anisotropy on the accuracy of the thin-walled beam dynamic model is revealed. The results show that the precise expression of shear flow has a significant effect on the modeling accuracy, and that the other coupled deformation terms have negligible effect.