Abstract: Based on the introduction to the mineralogical types and characters of bentonite, as well as its modification methods, including acid activation, roasting, inorganic salt adding and organic ammonium salt adding, this paper elaborates the present status of application of this mineral in wastewater treatment, garbage landfill site and amelioration of soils. Using bentonite as a reacting medium of permeable reacting barrier (PRB), the changing situation of groundwater pollution is simulated for landfill filtration liquid, with COD, sexivalent chromium and ammonium as target contaminants. The experiment shows that the pH and DO values have a certain influence on the removal efficiency of target contaminants. The removal rates of COD, sexivalent chromium and ammonium are 53%, 51% and 53% respectively, through the reacting medium. The result suggests the feasibility of bentonite as reacting medium of PRB.