The chelating reaction condition was studied between pig blood polypeptide and molysite.The ingredients of pig blood polypeptide-iron were also determined.The results showed that ferric chloride was suitable as iron source in chelating with pig blood polypeptide;the best condition was pH 5,the ratio of polypeptide and iron was 4∶1,solution concentration of polypeptide was 3.0%.The main contents of pig blood polypeptide-iron were polypeptide and iron with mass percents 70.02% and 12.23%,respectively.