Cable external arc is a serious ignition source for high-voltage power cables. Concurrently, the electric field generated by arc discharge can exacerbate cable combustion, leading to more severe consequences. Therefore, it is essential to investigate the influence of external arc on cable combustion characteristics. An experimental platform and a computational fluid dynamics model of cable combustion for external arc ignition of high-voltage power cables are built, and the process of arc ignition of cables is explored, and the model is verified based on the experimental results. The results indicate that under the action of an external 120 W arc, the cable is ignited at 87 s, which also verified the rationality of the cable combustion model. As the arc voltage increases, the combustion reaction on the cable surface intensifies. When the voltage amplitude reaches 3 kV, the maximum temperature of the cable sheath surface reaches 600K. After the cable is ignited, the flame on cable surface quickly spreads to both ends. When the arc voltage value increases to 5 kV, the maximum temperature exceeds 1200K and the flame has extended from 2 mm to 25 mm, making the cable fire more serious. The charged particles are mobilized by the electric field generated by the arc. This causes the reaction area to gradually move upward along the cable surface, resulting in the upward propagation of the flame.