Abstract: To delve into the formation process of single-pulse discharge arcs and craters in short electric arc machining (SEAM), observations and waveform acquisitions of single-pulse discharge arcs on pure tungsten and purple copper electrodes were conducted using high-speed cameras and multi-channel data acquisition devices. The characteristics of crater formation and material removal mechanisms were analyzed by combining electrode surface morphology with crater micro-topography. The study revealed that during the low-energy discharge, the arc around the purple copper electrode rotates with volume expansion, and the arc on the pure tungsten electrode is more stable compared to that on the purple copper electrode. During the high-energy discharge, the arc on the purple copper electrode protrudes at both ends of the cathode region, while the pure tungsten electrode contracts. The metal vapor was generated in the tool electrode, resulting in enhancing the stability of discharge arcs on one hand and increasing the crater size on the other hand. The discharge energy on the pure tungsten electrode is more symmetrical compared to that on the purple copper electrode.