Amino acids play an important role in organismsas the basic building blocks of proteins. The functions of amino acids with different group compositions and chiral structures are different, showing an urgent requirement to identify the basic chemical structure and molecular vibration information. This will provide an important theoretical basis for constructing basic biomolecule spectra and structural correlation models. NIR spectrum mainly shows the first overtone and binary combination vibration information of various hydrogen-containing groups (such as O—H, N—H, C—H, etc.). The vibration information is relatively complex, coupled with the resolution limitations of conventional infrared spectroscopy instruments and other reasons, resulting in a spectrum of experimental results. The band becomes wider, and its vibration mode cannot be accurately identified, making analysis more difficult. The theoretical calculation can independently calculate each vibration mode, providing clearer spectral information, and then analyze the wide absorption band obtained experimentally. This makes it easier to identify and analyze the structural vibration information of various groups in different molecular systems. In this work, the DFT calculation method carried out the structure optimization and anharmonic vibration analysis of three amino acids (glutamic acid, cysteine, glycine) and polypeptide (glutathione) composed of these three amino acids. The high-precision NIR spectrum of the four molecules in the band of 7 500～4 500 cm^-1 was calculated, and detailed band assignments were made, dividing the entire near-infrared band into three spectral regions dependent on the vibration intensity. Furthermore, the influence of structure and constituent groups on the spectral characteristics was explored, and the corresponding relationships between the spectra and the structure were established. Our research would provide ideas for a deeper understanding of the structural properties of amino acids and peptides.