Abstract: Three coagulants were selected to carry out deep phosphorus removal experiments. The influence of different factors on total phosphorus removal efficiency was explored in this paper. The results showed that different coagulants had a significant effect on the phosphorus removal efficiency of sewage, and the best phosphorus removal efficiency of PAC was 99% under the same dosage of coagulants. The pH value was the key factor affecting the deep phosphorus removal of coagulation technology. When pH was 7～8, the coagulant showed the best phosphorus removal effect, and the TP removal rate could reach more than 98%. In engineering application, the average TP concentration in effluent was 0.03 mg/L within the proper dosage range of PAC, so as to achieve the purpose of deep phosphorus removal. In view of the wastewater treatment project with low influent pH value, the phosphorus removal efficiency of coagulant could be significantly improved by adjusting pH value, and the average removal rate of TP would reach more than 98%, which provided an effective solution to the problem of water eutrophication. In addition, the purpose of this study was to optimize the coagulation reaction technology to provide a theoretical basis for engineering application, effectively improve the efficiency of sewage treatment and reduce operating costs.