The paper studies the coupled dynamical modeling theory of elastic beams in large overall motions based on the deformation theory of elastic beams and Hamilton's principle. The effect of large overall motion on the transverse and longitude vibration is analyzed and the striking effect of the coupled between the coupled deformation of midlines of elastic beams and large overall motion on the dynamic character of the system is obtained. Consequently, the coupling dynamical model of elastic beams in large overall motions is put forward.