Deep drilling and tunnel excavation rely on new rock-breaking technology. Currently, there is a lack of research on the micro mechanism of high-voltage electro-pulse boring (EPB). The design structure of the electrode bit is diverse, and there is still a great room for improving the service life of the electrode bit, the quality of the borehole wall, and the energy loss in the drilling process. Based on this, first, the electrode bits in the EPB system were improved, and the EPB tests was carried out. The three-dimensional (3D) reconstruction cloud graphs of broken granite were obtained, and the drilling with a diameter of 60 mm in granite and red sandstone was actualized. Compared with the drilling effect before improvement, the reliability and the service life of electrode bits and test devices were verified. Second, the high-voltage EPB experiments with different electric parameters were carried out, and the complete drilling with a diameter of 100 mm in red sandstone was realized. Finally, the composition and the microstructure of rock were obtained with Fourier-transform infrared (FT-IR) spectrometer, scanning electron microscope (SEM), and energy-dispersive spectrometer (EDS) before and after EPB. It was concluded that the prefragmentation could be realized by EPB. The rock mass near the discharge channel underwent an oxidation reaction in addition to physical damage and formed new oxidation products. The EPB experimental study provided practical guidance for the design of the electrical bits and the improvement of the rock-breaking efficiency.