In order to reveal the molecular mechanism of how high\|salinity aniline\|containing waste water affects the bacterial community structure, the PCR\|DGGE technique was used to analyse the change of the bacterial community structure acclimated to three different hypersaline aniline\|containing waste waters, with different content of chemical oxygen demand (COD), salts, phosphorus, nitrogen, chloride and aniline. The results were as follows. During acclimation to No. 2 waste water, the bacterial community diversity indices decreased when the concentration of waste water increased. During acclimation to No. 1 waste water, bacterial diversity was the highest in 5% waste water, while those in 20% and 40% were the lowest. During acclimation to No. 3 waste water, diversities in 0% and 5% of waste water were the highest, while those in 20% were the lowest. The different waste water compositions had different effects on the bacterial community diversity, indicating that adaptation and mutation might play important roles in the relationship between bacteria and their environment. The bacterial community diversity indices correlated negatively with the concentration of COD and salinity, but not with the concentration of chloride and aniline. The genetic variation of bacteria acclimated to three different high\|salinity aniline\|containing waste waters was very high: the percentage of polymorphic bands, Shannon′s informative index and Nei′s gene diversity index of bacteria acclimated to No. 3 waste water was the highest, while those of bacteria acclimated to No. 1 waste water took second place and those of bacteria acclimated to No. 2 waste water was the lowest. The genetic diversity indices were not significantly correlated with the concentration of COD, salinity, chloride or aniline. This suggested that the change of the bacterial community diversity might not due to a single factor rather to the integrated effects of all the contaminants in the waste water. The pairwise genetic distance between bacteria acclimated to five different concentrations of three different waste waters averaged 0.4724、0.4350 and 0.4902, indicating that the genetic variation induced to No. 3 waste water was the highest. Bacteria acclimated to five different concentrations of waste water could be clustered into two groups. During the acclimation to No. 1 and No. 2 waste water, bacteria acclimated to 0%, 5% and 10% waste water were clustered into one group while those acclimated by 20% and 40% wastewater were clustered into another group. Bacteria acclimated to 0% and 5% of No. 3 waste water were clustered into one group and those acclimated to 10%, 20% and 40% wastewater were clustered into another group. The change of the microbial communities could indicate a rapid adaptation of microorganisms to the change of the external environment.