Peptide foliar fertilizer (Pep) was prepared from edible gelatin by acid method. Then Pep was used as a chelating agent and iron sulfate was used as a iron source to prepare peptide chelated iron foliar fertilizer (Pep-Fe). FTIR, SEM, and TG were used to characterize and observe the structure and morphology of Pep and Pep-Fe separately, and the planting experiment was carried out. The reaction conditions for the preparation of peptide and peptide chelated iron were optimized based on peptide browning, amino nitrogen content and iron chelating rate. The results showed that the optimum reaction conditions were as follows: temperature 70 ℃, reaction time 7 h, mass ratio of gelatin protein to water 1:6, mass ratio of gelatin protein to concentrated sulfuric acid 1:1.25. The prepared peptide did not turn brown and the amino nitrogen content was 125.49 mg/ ml. Under the conditions of temperature 50 ℃, reaction time 1.5 h, pH4, and the mass ratio of peptide to iron sulfate of 2:1, the chelating rate of iron was 53.89%.