Knowledge of microbiological characteristics in the plant rhizosphere is essential for understanding the fate and transport of agricultural chemicals in soils. The present study was conducted to investigate the effects of an acetanilide herbicide napropamide on microbiological characteristics of tobacco (Nicotiana tabacum K326) rhizosphere soil and its dissipation behaviors under controlled conditions. The results showed that both microbial populations and enzymatic activities in rhizosphere soil were higher than those in non-rhizosphere soil. The populations of bacteria and actinomycetes decreased with napropamide addition in rhizosphere soil, while the populations of fungi displayed the decreasing, recovering and increasing trend throughout the incubation period. The activities of dehydrogenase and catalase were stimulated firstly, owing to napropamide addition, then were inhibited, and recovered to the control level, whereas the activities of urease were inhibited obviously during the testing stage. Napropamide rapidly dissipated in vegetated soil suggests that rhizosphere soil is a useful pathway to rapidly remove or detoxify herbicide residues.