Abstract: In this paper, the secondary effluent of a municipal sewage treatment plant in Jiangsu Province was taken as the research object. Through the simulation test and the pilot test of coagulation+air flotation deep phosphorus removal, the deep phosphorus removal effect of air flotation process instead of filtration process was explored. The results showed that FeCl₃ had the best phosphorus removal effect. When the molar ratio was 2.3, the TP of effluent could be reduced to 0.2 mg/L, and when the molar ratio was 7, the TP of effluent could be reduced to 0.05 mg/L; the process of air flotation had a strong dependence on PAM, so it was necessary to add PAM to ensure the effect of phosphorus removal and the stability of water quality up to standard. The concentration of PAM was 0.6 mg/L; when the reflux ratio was 20% and the dissolved gas pressure was about 0.6 MPa, the operation effect of the device was stable; through the analysis on the phosphorus components, it was found that the air floatation process had a good effect on the removal of suspended TP and phosphate, but no effect on the removal of non-coagulable phosphorus components.