To investigate the influence of bensulfuron-methyl (BSM) on culturable microbial quantities and unculturable microbial community structures, conventional and molecular biological methods were employed in five BSM treated soils with three replications, respectively. The results obtained with traditional culture-dependent methods showed that a low-level of BSM had slight and transient effects on culturable microorganisms; nevertheless, high concentration of BSM resulted in a dramatic decrease in bacterial colony forming units (cfus). The result obtained using denaturing gradient gel electrophoresis (DGGE) revealed that more than 17 bands were observed in low BSM contaminated soil samples and only 10 bands were detected in samples with high BSM contamination. In other words, the diversity of soil community structure is related to the concentration of BSM. Cluster analysis showed that the community structure under low level of contamination was more similar to that of the control, while heavy contaminated amendments were far away from the above group. In a sense, the cooperation of the traditional method and the molecular biological method is more powerful to study the soil microbial information in contaminated ecosystem.