In the magnetic suspension bearing system, the protection bearing, as its key component, plays a role in supporting the safe operation of the drop rotor after the failure of the magnetic suspension bearing, to protect the whole system from damage. Based on a multi-body dynamics simulation, this paper studied the characteristics of the protection bearing, such as the speed fluctuation of the rotor and the bearing inner ring, and the contact force between the rotor and the protection bearing when the 5-DOF rotor fell on the protection bearing. By adjusting the friction coefficient, the initial speed of the rotor, and other parameters, the movement process of the rotor falling in the protection bearing was studied. By comparing the speed fluctuation and contact force of the rotor and the bearing inner race, the influencing factors and rules of the impact of the rotor falling on the protection bearing were analyzed and summarized.