Abstract: Three sample plots of different habitat were selected in Yunnan and Sichuan to study effects of invasion of Eupatorium adenophorum on content of available nitrogen,available phosphorus and available potassium in soil.Results show that available nitrogen,available phosphorus and available potassium decreased by 33.9%,44.2%,and 32.2%,respectively,in Plot a; only available phosphorus did by 30.1% in Plot b;and no significant change was observed in Plot c.During the experiment,Plot a was found lower than the control in soil nutrient content,regardless of time period,and especially during the period from July to October of 2005,which suggests that the effect of the invasion of Eupatorium adenophorum varied from habitat to habitat,and was related to the growth rhythm of Eupatorium adenophorum.