Abstract: Compared with the floating frame of reference formulation, the absolute nodal coordinate formulation (ANCF) has significant advantages in dealing with the nonlinear large deformation problem of flexible bodies. ANCF defines the nodal co-ordinates in a global co-ordinate system, uses the global slopes instead of angles to define the orientation of the elements, has a constant mass matrix, and does not have the Coriolis centrifugal force. However,the elastic force matrix is a nonlinear term, and the solution will be time consuming and occupied resources. According to this,the elastic line method is introduced for solving the elastic force, the Green-Lagrangian strain tensor is defined on the centerline, the curvature formula is used to define the bending strain, and the torsion angle formula is used to define the torsional strain. At the same time, the finite element method is used to describe the displacement field of the three-dimensional flexible beam, and the constant mass matrix, the generalized stiffness matrix and the generalized force matrix of the beam element are solved, and then the dynamic equations of the element are obtained. The dynamic equations of the three-dimensional beam are obtained by the transformation matrix. Then the differences between the continuum mechanics method and the elastic line method are pointed out theoretically, and the dynamic simulation software is compiled. Finally, the dynamics behaviors of a flexible pendulum and a tracked vehicle are numerical investigated with the continuum mechanics method and the elastic line method. The results show that the elastic line method can effectively improve the calculation efficiency under the premise of ensuring accuracy.