Abstract: Ginseng black spot caused by Alternaria panax is one of the most important fungal diseases, seriously affecting the yield and quality of Panax ginseng. The inhibitory effect of eugenol on A. panax was investigated using the mycelial growth rate and the spore germination methods. The effects of eugenol on relative conductivity, malondialdehyde content, and antioxidant enzyme activities of A. panax were evaluated. The results showed that eugenol significantly suppressed the growth and development of the pathogen. When the concentration of eugenol was 0.30 mg/mL, the inhibition rates on mycelial growth and spore germination were 90.14% and 94.40%, respectively. After 12 h treatment with eugenol, the relative conductivity and malondialdehyde content (MDA) of A. panax increased significantly compared with the control, which was 66.18% and 1.83 nmol/g, respectively. The activity of peroxidase (POD), catalase (CAT), and superoxide dismutase (SOD) peaked at 24 h, with 379.80, 38.80, and 305.10 U/g respectively. Eugenol-induced programmed cell death exerts its antifungal function by damaging the integrity of the cell membrane, increasing lipid peroxidation, and promoting the accumulation of reactive oxygen species of A. panax. This study provided a reference for the rational application of eugenol in the green prevention and control of ginseng black spot, and increased the choice of fungicides.