Abstract: The yield,chemical components and relative contents of essential oil extracted from Eupatorium adenophorum Spreng by Soxhlet extraction and steam distillation were compared.The volatile chemical constituents of essential soil extracted were analyzed by Gas Chromatography-Mass Spetrometry.The results showed that the constituents of the volatile from the same plant and the relative contents were significantly different due to different extraction methods.For example,the relative content of α-bisabolol in leaf that collected from Guizhou was 1.99% and 7.55%,respectively,when it was extracted by Soxhlet extraction and steam distillation.The chemical components and their relative contents were significantly different in different plant organs collected at different time and in different locations.For instance,the content of gurcumene extracted from different leaf or seed in different locations was ranged from 0.41% to 5.23%.The experiment for pathogen inhibition showed that volatile oil from E.adenophorum had certain effect against four fungal pathogens tested .The inhibition rate was higher than 60% at the concentration of 3 000 mg/kg.The highest inhibition rate against Botrytis cinerea reached 80%.