Although rhizoremediation is an effective approach to remove organic pollutants from the environment, little is known about the mechanism of hexachlorobenzene (HCB) biodegradation in water. In this study, we used Typha angustifolia (T. angustifolia) grown in sterile Hoagland nutrient solution to determine the rhizosphere effects on the ability of bacteria in water to reduce HCB levels. The results revealed that T. angustifolia could facilitate HCB degradation and that the initial HCB concentration was the major factor responsible for HCB degradation in nutrient solution. Furthermore, HCB biodegradation in low-HCB nutrient solution with T. angustifolia fitted the first-order kinetics, owing to the high concentration of total organic carbon, low HCB toxicity, and unique bacterial community in the T. angustifolia rhizosphere. Denaturing gradient gel electrophoresis indicated that the rhizosphere effects and different dosages of HCB have significant effects on the bacterial communities by repressing and favoring certain populations. The most successful bacteria to adapt to HCB contamination was Bacillus sp., while the dominant bacterial phyla in HCB-polluted water were Proteobacteria and Firmicutes.