Red mud is generated as a by-product during the production of aluminum hydroxide from bauxite ore. In this study the red mud coagulants were prepared by reacting 100 ml of 5 M H2SO4 solution with 10g of red mud at 85 ℃ or by reacting 100ml of 9M HCl solution with 10g of red mud at 25 ℃. The prepared red mud coagulants were tested for their coagulation performance of pollutants in the municipal and industrial wastewater. In addition, the coagulation performance was compared with that of a commercially available coagulant (FeCl3). As a result, the red mud coagulants were found to have a good removal efficiency of pollutants in the municipal wastewater (turbidity, phosphate phosphorus) and in the plating wastewater (turbidity, Pb(2+), Cd(2+), Cu(2+), Zn(2+), Cr(3+)). In the experiment to remove COD in the petrochemical wastewater, the COD removal efficiency by the red mud coagulants was a little poor, but it was better than that by FeCl3.