The Bezier interpolation is introduced as a new discretization method for the rotating flexible beam deformation. First, the model of the rotating flexible beam is built. Then, the rigid-flexible coupling dynamic equations are established via employing the second kind of Lagrange's equation. The longitudinal deformation and the transverse deformation of the flexible beam are considered, and the coupling term of the deformation which is caused by the transverse deformation is included in the total longitudinal deformation; and a software package for the dynamics simulation of the flexible beam is developed. Finally, the simulation results of the Bezier interpolation are compared with those of the assumed method and the finite element method. Simulation results demonstrate that the computational efficiency of the Bezier interpolation is the highest, the computational accuracy of Bezier interpolation is in accordance with the needs of engineering, and is higher than the one of assumed mode method in high-speed case. The Bezier interpolation method is better than the assumed mode method in dealing with the large deformation dynamics problem. So the Bezier interpolation method will be hopeful to win popularity in the field of multi-body system dynamics.