This paper focuses on the effect of structural coupling in the behavior of composite rotor blade. We have searched for bending, extension and shear coupling term with the ply angle of rotor blade and the dynamic behavior of rotor blade for each coupling term. It was found that natural frequency increases as the rotating speed of rotor blade increases. In the couplings with feathering, bending coupling is main parameter, because bending coupling term is larger than shear . Also, the couplings with feathering is less effective in 0$^{circ}$, 90$^{circ}$, of ply angle and more variable at blade tip.