Based on the deformation theory of elastic beams,the coupling effect between the cou-pling displacements of a point on the middle line of beam and large overall motion is presented.The“coupling matrix library”and Jourdain’s variation principle and single direction recursive formulationmethod are used to establish the general coupling dynamical equations of flexible multibody system.Two typical examples show the coupling effect between coupling displacements and large overall mo-tion on the dynamics of flexible multibody system consisting of beams. Based on the deformation theory of elastic beams, the coupling effect between the cou-pling displacements of a point on the middle line of beam and large overall motion is presented. “Coupling matrix library” and Jourdain’s variation principle and single direction recursive formulationmethod are used to establish the general coupling dynamical equations of flexible multibody system. Two typical examples show the coupling effect between coupling displacements and large overall mo-tion on the dynamics of flexible multibody system consisting of beams.