Since distribution lines have relatively weak insulation compared to power transmission lines, it is more liable to lightning damages. This paper reports a study of how overhead ground wire height and impulse ground resistance affect the lightning protection performance. The results obtained in this paper show that high overhead ground wire worsen the lightning protection performance while reducing the impulse ground resistance improves the lightning protection performance. Therefore, it is recommended to set the overhead ground wire lower and take necessary measures to reduce impulse ground resistance. The results obtained also confirm the crucial role of the overhead ground wire as a protection of distribution lines.