In this study, in-depth processing of biologically-pretreated coking wastewater was performed using aluminum sulfate (alum) and alum + PAM, respectively, aiming to study removal efficiency of COD, SS and color of coking wastewater as a function of pH, alum dosage and/or PAM, and to determine the optimal conditions for treatment of the coking wastewater. It was found that the optimum dosage and pH are 300 mg/L and 6.5 for coagulation with alum. The optimal condition for coagulation/flocculation with PAM + alum was 15-minute reaction, pH of 6.5, alum dosage of 220 mg/L, PAM dosage of 6 mg/L. Coagulation using alum and PAM at the optimal condition was more efficient than treatment using single alum for removal of COD and color. Effluent COD after coagulation at the optimum conditions met requirements of the secondary standard described in “Integrated wastewater discharge standard”, while the corresponding color exceeded the limit. Hence, coagulation using alum was found to be inefficient in reduction of color for biologically treated coking wastewater.