This paper presents a new method to study the flying stabilities of air bearing sliders. Various forces on the slider are analyzed, and their work on the slider is calculated quantitatively. The contributions of the forces to the flying stabilities of the slider are evaluated according to their work on the slider. It is observed that the air bearing force plays a dominant role on the flying stabilities of slider, while the friction force and the intermolecular force do positive work, which destabilize the flying slider. In order to improve the flying stabilities of sub-5-nm air bearing slider, the friction force and the intermolecular force should be reduced as much as possible.