In this study, in-depth processing of biologically-pretreated low strength leachate was performed using aluminum sulfate (alum) and alum + PAM, respectively, aiming to study removal efficiency of COD, SS and color of leachate as a function of pH, alum dosage and/or PAM, and to determine the optimal conditions for treatment of the leachate. It was found that the optimum dosage and pH are 750 mg/L and 7 for coagulation/flocculation with alum. The optimal condition for coagulation/flocculation with PAM + alum was 25-minute reaction, pH of 6, alum dosage of 500 mg/L, PAM dosage of 5 mg/L. Effluent quality after coagulation at the optimum conditions didn’t met requirements of the tertiary standard described in “Integrated wastewater discharge standard”. Coagulation using alum was found to be inefficient for advanced treatment of refractory leachate after biological treatment.