The reignition of aero-engine combustors at high altitudes poses significant challenges due to the low-temperature and low-pressure environment. A novel Long Pulse-Width Plasma Ignition (LPWPI) system has been developed to enhance ignition performance. The LPWPI system can effectively prolong the discharge duration time, improve ignition efficacy, and increase the plasma penetration depth. Experimental comparisons with the traditional Spark Ignition (SI) system demonstrate that the LPWPI increased discharge duration to 2.03 ms, which is 45 times longer than that of the SI system, while also doubling the spark penetration depth to 24.1 mm. The LPWPI system achieved a discharge efficiency of 61.1%, significantly surpassing the SI system’s efficiency of 23.3%. These advancements facilitated an extension of the lean ignition boundary by approximately 22.7% to 39.3%. High-speed camera recordings reveal that the spark duration of the LPWPI system was extended to 2.1 ms, compared to 0.6 ms in the SI system. Ignition progress with LPWPI shows a sustained spark kernel without the flame residence stage observed in the SI system. The impressive performance of the LPWPI system suggests that it is a promising alternative for aero-engine ignition systems.