This study was conducted to find out environment-friendly disease control method to Alternaria blightcaused by Alternaria panax of ginseng. For this study, 150 methanol extracts from medicinal plants were evaluated and theextract of Impatiens balsamina showed most strong antifungal activity against A. panax. The methanol extract of I. balsam-ina showed also stable antifungal activity against other ginseng pathogens such as Botrytis cinerea and Fusarium sp., whentreated by heat or pH. In vivo, Alternaria blight incidence rate was low of 13% with the treatment of I. balsamina methanolextract compared to 35% of the non-treatment. The antifungal compound of I. balsamina was purified and identified byusing a silica gel column chromatography, TLC and ESI-LC/MS/MS analysis. The compound which showed strong antifun-gal activity was identified as 2-methoxy-1,4-naphtoquinone (C11H8O3).