Angular contact ball bearings are widely used in the multiple rotor system, such as gear box, machine tool spindle, and aero-engine rotors. The support stiffness is very important to the vibration of shafting. In order to obtain the dynamic stiffness, a numerical simulation method for dynamic stiffness of angular contact ball bearings is presented. By means of LS-DYNA software, the displacement and stress curves of the bearing’s different components are obtained successfully, and then, the dynamic stiffness of bearing under certain working conditions also can be calculated. The maximum envelope radius of the inner ring of the measured bearing can be taken as the relative displacement change value of the inner and outer rings of the bearing. To obtain the dynamic stiffness, the test strategy for dynamic stiffness of the angular contact ball bearings is introduced. The experimental results show that the equivalent dynamic stiffness increases with the increase in the preload of measured bearing under certain conditions. The simulation result coincides with the experiments well. The research work can provide the basis for the design and dynamics analysis of the bearing rotor system and have important engineering significance to improve the service performance of angular contact ball bearings.