Through pot experiment,effects of phytoremediation on microbial communities in soils different in nickel treatment level were studied.Two Ni hyperaccumulators and one Ni tolerant species were planted in paddy soils different in Ni concentration,ranging from Ni 100 to 1 600 mg kg^-1.After 110 days of incubation,soil microbial activities were analyzed.Results show that populations of bacteria,fungus,and actinomycetes and biomass of the microorganisms were stimulated when nickel was added at a rate of Ni 100 mg kg^-1 in nonrhizospheric soil.When the rate was over Ni 100 mg kg^-1 in the soil,adverse effects on the soils microbial communities were observed.Plantation of hyperaccumulators could increase both the population and biomass of soil microorganisms,because by absorbing nickel from the soil and excreting root exudates,the plants reduced nickel toxicity and improved the living environment of the microbial.However,different plant species had different effects on microorganisms in soil.Randomly Amplified Polymorphic DNA (RAPD) with 5 primers was used in this study in 25 soil samples of 4 types of soils.A total of 947 amplified bands were obtained,including 888 bands of polymorphic and 59 bands of nonpolymorphic.The results indicated that the composition of microbial DNA sequences had changed because of nickel addition in treated soils.Shannon-Weaver index of soil microbial DNA sequence reduced in nickel contaminated soils with increasing nickel concentration.The changes in Shannon Weaver index in the 4 types of soils ranged from 1.65 to 2.32 for A.corsicum,1.37 to 2.27 for A.murale,1.37 to 1.96 for B.juncra,and 1.19 to 1.85 for nonrhizospheric soil.With the same amount of nickel added to soils,the Shannon-Weaver index in rhizospheric soil with plant was higher than that in nonrhizospheric soil.