Lightning is a major cause of tripping faults in overhead transmission lines. Multi-chamber lightning arresters are widely used to protect high-voltage lines from lightning because of their reliable arc-quenching performance. This paper analyzes the development and quenching process of an arc after a lightning breakdown arrester and studies the quenching mechanism of a multi-chamber arc structure based on its structural characteristics. We built an impulse-current test platform and carried out an impulse-current test for the multi-chamber arrester. The arc motion was captured by a high-speed camera, and the height, speed, and temperature of the arc ejection were obtained by signal processing. The multi-chamber arrester structure is optimized by using the maximum arc ejection height and the maximum ejection speed as metrics to find the optimal combination of the quenching-hole diameter and depth and the gap distance of the multi-chamber structure.