Abstract: The surface topography of EDM can be improved by ultrasonic vibration, but the addition of ultrasonic vibration also makes its material removal mechanism more complex and difficult to standardize the process. In order to understand the process characteristics of axial ultrasonic vibration-assisted EDM more comprehensively, EDM milling and axial ultrasonic vibration-assisted EDM milling were carried out on TC4 workpieces respectively. Different peak currents, pulse widths, pulse gaps, and ultrasonic amplitudes were selected to conduct one-factor experiments and analyze the surface roughness Ra. The results show that the introduction of axial ultrasonic vibration into the EDM milling process can reduce the surface roughness by 5.5%-18.9%, and the addition of axial ultrasonic vibration changes the energy distribution relationship between poles and results in a reduction of the energy used for material removal. This study can provide data support for the theoretical analysis of axial ultrasonic vibration-assisted EDM milling process, and provides an important reference for the selection of process parameters.