Micro electrical discharge machining (EDM), enhanced with ultrasonic vibration, is explored and assessed as a method for developing microelectrode array, for microelectrode array fabricated by LIGA has shortcomings such as complex technology and high price. Based on the mechanism of micro-EDM, micro-hole array discharges to fabricate microelectrode array by reverse copying. In the process of reverse copying, the thicker rod electrode can not rotate, resulting in electric arc and short-circuit occurring easily, so it is necessary to add ultrasonic vibration on the plane plate electrode, in order to exclude debris as soon as possible and stabilize machining process. In the process of machining, four parameters, such as working voltage, working capacity, ultrasonic amplitude and holes spacing, are important to machining efficiency, each parameter has four typical values. In order to reduce experiment times, a scheme of orthogonal experiment was designed with different parameters combination. With result of experiments, the ratio of mean square deviation to error mean square deviation of each parameter was calculated and significance of each parameter was obtained, and the best parameters combination was asserted through theoretical calculation. Also, experimental study of using microelectrode array to machine micro-hole array by Micro- EDM was made and influence curve of each parameter was drawn. Finally, 5×5 arrays of microelectrode were obtained, the diameter of single electrode is less than about 30.m and heightto- width aspect ratios is more than 8, moreover, these microelectrode arrays have good coaxiality and surface quality.