A compound flocculant, Poly aluminous-ferric-sulphate (PAFS), was prepared with waste slag of a steel work, hematite tailings, concentrated sulfuric acid and fly ash .And it was one-step synthesized with different mole ratio of Fe (Ⅲ)/Al (Ⅲ). The description of product was sticky red liquid and yellow-green solid. Its concentration was 1.45～1.65g/ml, and the concentration of ferric ion is higher than 160g/L, aluminum ion between 10.29g/L and 99.18g/L, the basicity is higher than 12%. According to Ⅴ inferior quality water of DaLaTe plants from Yellow River (the third quarter of Baotou hedong district) we select products with Fe (Ⅲ)/Al (Ⅲ) mole ratio is 10:5. And product PAFS nearly 4 tons in the self-reaction kettle.