Water plays an important role in nearly every aspect of geological processes as well as in the evolution of planetary bodies. Chang E-3 NIR spectra appeared weak peak of OH in the vicinity of signal 1.4 μm, it may represent the presence of water. In order to quantitatively calculate the water content, apatite as the research object in the paper. Through analyzing and validating the infrared spectrum correlation between 1.4 μm and 2.8 μm of the structure water in the apatite, we obtained its molar absorption coefficient in the infrared spectrum of 1.4 μm. IR spectra were collected on oriented. When the light vector E is parallel to the c-axis of the apatite crystal, H₂O concentration in apatite can be related to measured IR absorbance as follows: C=ωA/ερd, which based on Beer-Lambert’s law. This result can provide reference for the interpretation of Chang E-3 near-infrared spectral data of water signal. This method can provide the basis for the quantitative calculation of structure water in the near infrared spectrum in other moon minerals.