Abstract: The ethanol extracts from 5 Artemisia plants, including A. dubia, A. palustris, A. argyi, A. carvifolia and A. capillaris, were used to screen the active ingredients for the inhibition of Phytophthora infestans. The antifungal activities of ethanol extract of Artemisia plants against 2 strains of P. infestans(pn5502 and pn7604) were measured by radial growth assay, and the antifungal active component of ethanol extract of A. dubia was tracked by silica gel column chromatography. The findings indicated that at the concentration 1 mg/mL, all the tested extracts showed some degree of antifungal activities against the 2 strains P. infestans, and extract of A. dubia showed prominent antifungal activity with inhibition rate of 89.04% and 71.38% against pn5502 and pn7604, repectively. At the concentration of 0.5 mg/mL, the inhibition rate of Fr₁ to both strains was up to 100%. The EC₅₀ of Fr₁ for pn5502 and pn7604 were determined by different concentration gradients test, they were 7.4733 g/mL and 9.4634 g/mL, respectively. The study concluded that the ethanol extracts of 5 species of Artemisia plants showed different degrees of antifungal activities against 2 strains of P. infestans. Fr₁ of A. dubia showed the most significant antifungal activity, which was more effective than that of the positive control(cymoxanil·mancozeb), therefore the antifungal active components of A. dubia are worth further investigation.