Abstract: In order to improve the high-value utilization of Spirulina platensis, the chelating conditions of Spirulina platensis protein peptide were preliminatively optimized with ferrous chloride as the iron source. The chelates were characterized by molecular weight determination, amino acid composition experiment, fluorescence spectrum, scanning electron microscopy and quantum chemical calculation. The results showed that the suitable chelating conditions were pH6, mass ratio of ferrous peptide 6:1, concentration of peptide solution 1%, temperature 60 ℃ and time 40 min. Under these conditions, the chelating yield was 44.13%. The peptide of Spirulina platensis produced a new structure after chelating with ferric salt. Iron was mainly combined with the carboxyl group of glutamic acid and aspartate, the amino group of arginine and the guanidine group of lysine, and was embedded in the cavity formed by the electronegative end of amino acid to form a stable structure, which proved the formation of chelates. The research results would provide a theoretical basis for the development of Spirulina platensis iron supplement.