Precision ultrasonic vibration cutting is a promising technology in field of precision and ultra-precision machining. It is a kind of the pulsing cutting process with a constant vibration frequency and sine-wave amplitude of vibration. In this article, a rational model of cutting force in vibration cutting is established, and the vibration cutting mechanism is analyzed. Specially, by the method of numerical simulation, the effect regulation of amplitude of vibration on cutting force is theoretically discussed for the first time in precision vibration cutting. And the relationship between cutting parameters and cutting force is probed into on the different cutting conditions.