Polyferric silicate sulfate flocculants were prepared by using tetraethylorthosilicate and polyferric sulfate as raw materials. The relevant mechanism was studied. And it was found that since tetraethylorthosilicate had the characteristics of slow hydrolyzation, the reaction was easy to control. Thus, the products had a good repeatability, which was better for the study of algae removal. The optimum preparation conditions of polyferric silicate sulfate were determined by using orthogonal design, in which Fe/SiO2 mole ratio was 1, polymeric temperature was 50 ℃ and polymeric time was 60 minutes. Furthermore, the optimum conditions of removals algae were determined as well, in which when the pH of raw waste water was 11.0, the dosage of PFSS prepared in the optimum condition was 24.1mg/L and the dosage of preoxidation was 0.7mg/L.