Abstract: By using the sodium silicate and waste hydrochloric acid as raw materials, polysilicic acid is prepared. The study shows that, under the conditions of the concentration of sodium silicic acid being 4%-8%，the pH＜4， and the reaction time being about 5 hour, the stable polysilicic acid is made. The polysilicic acid is compounded with polyferric chloride sulphate under certain conditions, then the polysilicic acid-polyferric chloride sulphate flocculence is prepared. The study shows that： when the Cl-/SO42-molar rate is 1∶1, the Fe/Si molar rate is 2∶1, the flocculence has the best effect on paper-making waste water treatment. This research takes the trash? as raw material, compounds a new flocculating admixture, then utilizes it to process the paper-making waste water for the purpose of initiating the circulation economy.