Abstract: Using polysodium p-styrene sulfonate and silane coupling agent (KH560) as modifiers, red mud was modified by sulfonation and coupling, and used in the adsorption treatment of landfill leachate. The effects of pH value, dosage of adsorbent, adsorption time and reaction temperature on the adsorption of COD and ammonia nitrogen were studied. The modified red mud was characterized by infrared spectroscopy and scanning electron microscope and the isotherm, kinetic and thermodynamic of adsorption were also discussed. The results showed that the adsorption effect of red mud modified by sulfonation coupling (SCRM) on COD and ammonia nitrogen in leachate was significantly improved. At the conditions of pH value 8, dosage of 60 g/L, adsorption time of 90 min and reaction temperature of 20 ℃, the equilibrium adsorption capacity of COD and ammonia nitrogen were 81.51 mg/g and 19.24 mg/g, and the removal rate reached 87.57% and 72.05%, respectively. The pore structure of red mud particles changed from shallow pores to penetrating pores, and obvious sulfonated characteristic groups appeared after modification. The adsorption of COD and ammonia nitrogen by SCRM belonged to monolayer adsorption and multilayer adsorption, respectively. The adsorption kinetics of the two adsorption processes were more consistent with the pseudo-second-order kinetic model, and both were endothermic and entropic spontaneous reaction processes.