Spin exists in high-speed transmission support bearings, which can affect oil film thickness of bearing. The calculation formulas on oil film stiffness of angular contact ball bearing by considering spin was deduced based on the elastohydrodynamic lubrication theory (EHL) and the method on calculating attitude angle by Darren Bell theory, considering the changes of the minimum oil film thickness on the contact points between balls and raceways when spin exists both in inner and outer raceway. And an example was calculated and compared with the stiffness which was calculated by the minimum oil film thickness experienced formulas proposed by Hamrock-Dowson and unconsidered spin. The calculation results show that the spin angular velocity increases with the rotary speed increases but decreases with load increases, the radial load more impacts on the spin and the axial load less. The minimum oil film thickness which is considered spin is smaller and the oil film stiffness is bigger due to the effects of sliding velocity after considering spin. It is necessary to consider the impact of the spin on bearing stiffness when calculating the high-speed transmission shafting vibration.