Abstract:As far as the hard and brittle materials were concerned, the traditional methods of materials processing is usually very difficult to handle.The current density produced by electric arc machining is much greater than that of electrical discharge machining, so the electric arc machining has higher processing efficiency than electrical discharge machining. According to the characteristics of hard brittle materials, a kind of rotary ultrasonic vibration assisted electric arc processing machine tool was designed in this paper. The machine adopt “C” type structure that is composed of machine table and numerical control system. The design of the machine tool is mainly composed of three axes X-Y-Z, ultrasonic rotating spindle, servo motor, marble table, pillar and working liquid trough. The numerical control system is mainly composed of the switch controller, motion control card, servo drive, pulse generator, ultrasonic generator, and industrial control computer. The small hole micro-graphs were studied by this device with different thickness of spring alloy steel. The small hole micro-graphs were analyzed by Mat-lab for small hole edge detection and roundness calculation and compared with each other. The results show that the cavities processed by ultrasonic vibration are better and the edges are smoother.