In this paper, geometric nonlinear dynamic model of spatial slender beam with large deformation is established, and then a dynamic experiment is carried out to verify the correctness of the dynamic model. Firstly, the position and the attitude of the cross-section of the beam is described by 3 absolute position coordinates and 3 rotational angles, and then based on the assumption of the coincidence of the tangent of the neutral axis and the normal vector of the cross-section, the number of the generalized coordinates of each node is reduced. Variational dynamic equations of the spatial slender beam are derived based on virtual work principle. Comparison of the simulation time of the geometric nonlinear model and LS-DYNA software verifies the efficiency of the formulation. By leading into kinematics constraint equations, dynamic equations of the hub-beam multibody system are obtained. In case of large deformation, experiment of the rigid-flexible coupling system composed of an air-bearing test bed and a spatial beam is carried out to verify the correctness of the geometric nonlinear model of spatial beam.