A study on ultrasonic vibration-assisted electrical discharge machining (UVEDM) micro-hole, which mainly includes three key designs, was conducted to improve the machining performance of the electric discharge machining (EDM) micro-holes on TC4 titanium alloy. First, a mathematical model for the velocity of the flow field in the interelectrode gap was established. Consequently, the effect of the presence or absence of ultrasonic vibration on the flow velocity was analyzed. Furthermore, based on COMSOL Multiphysics, the two distributions of the flow field and the debris in the interelectrode gap were simulated and the influence of ultrasonic amplitude on them was analyzed. Finally, the study of UVEDM micro-hole machining with different ultrasonic amplitudes was conducted. The machining performance of the UVEDM micro-hole was found to increase with the increment of the ultrasonic amplitude and the optimal value of 5.22 µm, while the performance decreases when the ultrasonic amplitude goes beyond the optimal value. Compared with EDM micro-hole, the MMR is increased by 2.4 times, and the electrode loss and hole taper are reduced by 56% and 24%, respectively.