This paper has studied phosphorus removal effects of ferric chloride (ionic state), polyferric chloride (polymer state) and ferric hydroxide (gel state) on the effluent of a municipal sewage treatment plant. The total phosphorus (TP) in the effluent was 1.74 mg·L-1. Results showed that ferric chloride was the best phosphorus remover among the three forms of ferric salt coagulants. With a dosage of 40 mg·L-1, its phosphorus removal rate could reach 90% and TP in the treated wastewater was reduced to less than 0.17 mg·L-1. After the treatment, the effluent quality met the first level A criteria in the Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant (GB18918-2002). At the same doage of 40 mg·L-1, the phosphorus removal rates of polyferric chloride and ferric hydroxide were 62% and 59%, respectively, lower than the rate of ferric chloride.