Ultrasonic machining is a non-conventional machining process. Ultrasonic machining offers an effective alternative for ultra precision machining of hard and brittle materials due to its unique characteristics. This paper did a comprehensive analysis on ultrasonic machining mechanism in theory. The experiment compared this ultrasonic machining process with the common machining process in surface quality is done and the experimental result show that the smooth high quality surface can be obtained under ultrasonic machining.