Abstract: Abstract: Through the analysis of sampling, the effects of exotic species Flaveria bidentis invasion on soil microbial communities, enzyme activities and nutrients around their roots in non-cultivated land and cultivated land and around maize roots were studied in order to reveal the mechanism of Flaveria bidentis invading farmland and barren land successfully. Our experiment analyzed the cultivable soil microbe populations, soil available nutrients and soil enzyme activities around the roots in both non-cultivated land and cultivated land when Flaveria bidentis invaded. In Flaveria bidentis root surface in the non-cultivated land and cultivated land, the contents of available N , P and K are 4.44, 6.88 and 2.64 and 5.31, 13.78 and 7.56 times as those in the nude land (CK) respectively. The numbers of cultivable bacteria, fungi and actinomycetes in root surface are 13.23, 6.67 and 21.40 and 9.27 , 2.15 and 2.24 times as those in the nude land respectively. The alkaline phosphatase, acid phosphatase, urase, dehydrogenase, invertase activities are 19.44, 5.39, 1.64, 1.74 and 4.62, and 2.26, 3.45, 1.53, 0.95 and 4.89 times as those in the nude land respectively which can indicate that bacteria are so active. In soil of maize root surface, the contents of available N, P K nutrients at non-interactional root surface are 63.54%, 64.70% and 80.71% of that at interactional root surface. The above-mentioned results suggest that the root secretion of Flaveria bidentis increases the quantity of cultivable soil microbe groups, soil enzyme activities and available nutrients contents around their roots, reduces the quantity of cultivable soil microbe groups, soil enzyme activities and available nutrients contents around maize roots growing nearby under the natural environment, which may be one of main factors making Flaveria bidentis invading farmland and barren land successfully.