Ultrasonic vibration electrical discharge machining (UEDM) in gas is proposed in this paper. It is shown that electrical discharge machining with ultrasonic aid can be achieved well in gas medium. The tool electrode is formed to be thin-walled pipe, and high pressure gas medium is supplied through it. During machining, ultrasonic vibration of workpiece can improve the machining process. The molten workpiece material can be ejected out from base body of workpiece with the aid of ultrasonic vibration and be removed/flushed out of the working gap without being reattached to the electrode. A theoretical model to estimate the material removal rate has been developed. Selecting 45# steel and copper as the workpiece material and electrode material, respectively, experiments have been carried out, the results showing that UEDM is a method with a high material removal rate (MRR). The greatest advantages of this technique are lower pollution and low electrode wear ratio.