A new composite coagulant polymeric aluminum ferric sulfate (PAFS) was synthesized using FeSO4·7H2O and Al2(SO4)3 (industrial) by the direct oxidation method. The optimization of preparation process of PAFS was investigated using single factor and response surface methodology based on Box-Behnken central design. Parameters affecting the coagulant performance, such as reaction temperature, time, SO4 2-/Fe, NO3 -/Fe, Al/Fe, PO4 3-/Fe, and OH/Fe molar ratios were examined. The results show that when temperature, time, SO4 2-/Fe, NO3 -/Fe, Al/Fe, PO4 3-/Fe, and OH/Fe molar ratios were 84℃, 48 min, 0.38, 0.47, 0.11, 0.14, 0.03, respectively, it is the optimum conditions for synthesis. In this condition TP removal was 98.67%, and the experimental results were in good agreement with the predicted values of the model equation with 0.38% deviation. Furthermore, COD (chemical oxygen demand) and turbidity removal efficiency were 79.13% and 98.12%, respectively.