The best synthesis conditions for preparing PFAC (polymeric ferric aluminum chloride) were studied  by using  Hebei Yongnian local waste hydrochloric acid pickling liquor.When 100 mL waste pickling liquor is used as a benchmark, the reaction time is 1 h, the reaction temperature is 70 ℃, the amount of oxidant n (Fe2+) ∶n (H2O2) = 1∶1.0, the dosage of calcium aluminates powder is 4 g,the PFAC, which the total effective composition content is 18.14% can be obtained. The PFAC was used in simulated sewage treatment, when the addition amount of PFAC is 4 g/L, reaction temperature is 30 ℃, pH is 7, the chroma removal rate is 81.69%, turbidity removal rate is 80.78%, the COD removal rate is 65.48%, the content of phosphorus removal rate is 35.88%.