Measuring surface reflectance is crucial for studying the spectral characteristics of ground objects and inspecting satellite surface products. This paper uses a ground spectrometer to measure the sand surface reflectance in the Ali region of the Qinghai-Tibet Plateau, and studies and analyzes its typical spectral characteristics. Conduct authenticity testing and error impact analysis on the surface reflectance products (MOD09/MYD09) and surface albedo products (MCD43 A4) generated by the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard the Terra and Aqua satellites. The results indicate that the Gobi in the Ngari region exhibits typical sand spectral characteristics. The surface reflectance values in each band range from 0.08 to 0.35. The surface reflectance in the 300～700 nm spectral range increases with the wavelength, while in the 750～1 750 nm spectral range, the surface reflectance also increases with the wavelength. The surface reflectance changes less in the nm spectral range. Compared to my country’s sand reflectance of the Dunhuang radiation correction field, the spectral curve is very similar, and the spectral angle is 2.18°. The observation geometry and atmospheric lighting conditions influence the results of the star-ground comparison. The validation accuracy of the afternoon star Aqua product is superior to that of the morning star Terra, with an average error of approximately 5%, aligning with the official nominal accuracy of MODIS. Research shows that the spectral characteristics of the sandy land in the Ngari area are stable and representative, making it an ideal site for on-orbit radiation calibration and inspection of our country’s optical satellites.