Taking the central rigid body and flexible beam as examples, the dynamic modeling of the rigid-flexible coupling system lacking a strong component of mass and inertia is studied in this paper. The simulation results show that the established model can explain the cause of the dynamic stiffening phenomenon and calculate the system frequency at different rotating speeds, which can accurately explain the dynamic stiffening phenomenon of the rigid-flexible coupling system. At the same time, considering the translational motion of the central rigid body, the influence of the mass and inertia of the rigid body on the attitude angular vibration frequency of the system after maneuvering is obtained.