Phosphate adsorption capacities of different natural bentonites, including seven samples, in phosphate-contaminated waters different in phosphate concentration were investigated, and the mechanism of phosphate adsorption onto bentonite was discussed by adsorption isotherm experiment. Results showed that phosphate adsorption capacities of seven natural bentonites were different in waters different in phosphate concentrations, and also did the same genotype bentonite with different mineral constituents. In water of Grade V (P 0.4 mg/L) and Grade V-minus (P 1.0 mg/L), BN-2 had the highest adsorption capacity, BN-6 had the poorest adsorption capacity, while other bentonites had great different phosphate removal efficiencies, due to their discrepant composition. The phosphate adsorption isotherm of natural bentonites was fitted to the Freundlich equation in terms of R2 values. It suggested that the adsorption process of phosphate on bentonites was inhomogeneous multilayer adsorption. The results depicted above revealed that different natural bentonites should be choosed in practical application, in view of their characteristics, to make them effectively applied.