The friction driving principle of ultrasonic motors is a complex issue. In this paper, tangential motion and normal motion of the particle in the drive-foot of the stator are analyzed. Equal speed points (ESPs) are defined as where the transverse velocity of the particle is equal to the velocity of the slider. The elliptical arc contacted with the slider is divided by ESPs into the driving-arc and hindering-arc. When the motor works, the center of the stator mass vibrates as the longitudinal vibration of the stator. Force applied to the end of the stator is not a constant value because of this vibration, and the slider is driven intermittently by the stator. Friction between the slider and stator is influenced by factors such as preloading, stiffness of materials, or stator vibration. The analysis on driving and the motor′s friction can also provide a reference for ultrasonic motors