As the key part of the train bogie,the rolling bearings with pedestal looseness will directly affect the vehicle running safety and smoothness. For the problem of the high-speed train rolling bearing subjected to looseness faults on the fitting surface between inner ring and shaft neck,the vertical coupled dynamic model of high-speed train car body-frame-suspension-rolling bearing-wheel/rail is proposed. Optimized Runge-Kutta numerical integral method and experimental method is constructed to study the nonlinear dynamic characteristics of the coupled system of high-speed train rolling bearing with pedestal looseness under different loosening clearance and speeds. The result shows that the theoretical calculation fit well with experimental results,and the size of the looseness gap value has negligible effect on the vibration response of the axle box on the side without loose,but it has a great influence on the vibration response of the loose axle box. The system motion state will be changed,which the nearly quasi motion turn to chaotic motion. When the train travel at low speed,the vibration amplitude and vibration velocity of the loose axle box is greater than that of its high speed. The low frequency component of the vibration response of the axle box is only related to the speed,which doesn’t change with the change of the looseness gap value.