Most electrical fires are caused by single-phase grounding fault of cable, so it is of great significance to study the process of arc igniting cable and the development process of cable fire. In this paper, a single-phase grounding arcing experiment platform is built, and the parallel arc ignition experiment of XLPE cable in case of single-phase grounding fault is carried out, and the process of arc igniting cable and its ignition characteristics are analyzed. FDS is used to simulate the cable trench fire, and the development and spread laws of cable trench fire are summarized. It is found that the arc current is determined by the circuit parameters, and the arc resistance and arc power increase with the increase of electrode distance. The AC arc appears “arc burning peak” after the current zero crossing and “arc quenching peak” before the current zero crossing, and the former is higher than the latter.