Abstract: Aiming at the problems of difficult remove of debris, low machining efficiency and serious electrode wear when conventional EDM machining TC4 titanium alloy micro-holes, the experiments on the ultrasonic vibration assisted EDM of titanium alloy micro-holes were carried out. By changing the ultrasonic vibration amplitude and electrical machining parameters, a single factor experiment was carried out with the material removal rate, relative electrode wear rate and hole taper as the process indicators, and the influence law of each machining parameter on the above indicators was summarized. The results showed that under the same electrical parameters, using ultrasonic EDM, the material removal rate is 3~5 times higher than that of conventional EDM, the RTWR and taper are reduced by 55%~80%, respectively. The phenomenon of abnormal discharge will be reduced when pulse is increased, resulting in a corresponding decrease in material removal rate. The gap voltage should be selected between 90~120 V, if gap voltage too small, it is not conducive to debris removal and deionization, if gap voltage is too large, the aperture will be too large and the dimensional accuracy will be reduced.