Abstract: In order to characterize the structure of peptide chelating calcium prepared from catfish flesh and bone paste,the structure of the peptide and peptide chelating calcium was analyzed and compared,ultraviolet absorption spectrum,infrared absorption spectrum,scanning electron microscopy and X-ray photoelectron spectroscopy were used in the experiment. The results showed that,the maximum ultraviolet absorption peak of peptides chelating calcium had a red shift,the N-H stretching vibration absorption peak showed a blue shift,and the N-H stretching vibration absorption peak for amide II disappeared,meanwhile there was a red shift in C=O stretching vibration absorption peak,and the deformation vibration fingerprint region for O-H disappeared,compared with that of polypeptide,suggesting an integration of calcium ions with amino and carboxyl of the peptide. After chelation with calcium,the microstructure of polypeptide turned out to be compact and regular,and the elements Ca and Mg emerged in the surface of peptide chelating calcium. The results of the study provided theoretical supports for further study on structure-activity and application of peptide chelating calcium derived from enzymatic hydrolysis of catfish flesh and bone paste.