Abstract: Mangiferin is an active ingredient of traditional Chinese medicinal herb Anemarrhena asphodeloides.Bioassay tests in vitro showed that mangiferin could inhibit the mycelium growth of Phytophthora infestans intensively,with EC50 value 32.65 μg/mL,but it has low inhibitory effect on the zoospore release of P.infestans with EC50 value 100.97 μg/mL.Coomassie brilliant blue G-250 colorimetric method was used to test the protein variations of P.infestans mycelia.The result indicated that mangiferin inhibited the protein biosynthesis of P.infestans.It could influence the permeability of the cell membrane of P.infestans at higher concentration,but the effect was not significant at the lower concentration 12.5 μg/mL.Dissolved oxygen content in zoospores suspension was used to test the respiratory inhibition effect of mangiferin on P.infestans.The results revealed that mangiferin had significant inhibition effect on metabolic pathways such as glycolytic pathway (EMP),tricarboxylic acid cycle (TCA) and hexose monophosphate pathway (HMP),and the inhibition effect on HMP was the most significant.