Algae in the estuary of the Nanfeihe River show high concentrations in the summer and autumn, and the concentration of NH⁺₄-N is extremely high in the winter. Based on these characteristics, we studied the efficiency of the enhanced coagulation technology in removing algae and NH⁺₄-N, and applied this technology to an on-site coagulation and sedimentation system by the river. The results show that polyaluminum chloride(PAC)had the highest removal rate(76%)of algae when the coagulants were applied alone; the removal rate increased markedly when cationic polyacrylamide(CPAM)was applied as coagulant aid and the removal rates of algae all reached 99%. However, they had little effect on the removal of NH⁺₄-N. Joint use of polyaluminum ferric chloride(PAFC)and CPAM had the highest removal rate(7. 54%)of NH⁺₄-N. Clay mineral was also chosen to increase the removal rate of NH⁺₄-N. The attapulgite modified by NaCl and MgCl₂ was used in combination with CPAM, and the removal rate of NH⁺₄-N reached 85. 65%. PAFC+CPAM was selected as a pharmacy prescription used in the on-site coagulation system. The mean removal rate of algae was 88. 64% in the summer and autumn and that of NH⁺₄-N was 24. 49% in the winter.