Ten typical radiometric calibration sites are selected for radiometric calibration and instrument performance tracking in northwest China. Simultaneous observation of reflectivity spectrum is realized by ground hand-held spectrometer and low-altitude unmanned aerial vehicles (UAVs)during satellite transit. The reflectance spectral differences of multiple sites are compared systematically, and the spectral characteristic analysis and parameter modeling of multiple sites are carried out. The spectral shape of the same site varies little at different time in one day, and the spectral angle is less than 5°. The variation of spectral amplitude is mainly affected by solar zenith angle and atmospheric conditions, and the spectral amplitude varies little at the same time in different days. The spectral shapes and amplitudes of different sites are quite different. The spectral curves of the same site at different observation scales are basically the same. Through the analysis, it is found that when the wavelength is less than 1100 nm, the spectral curves of all desert sites are similar to the curves of triangular arctangent function. Based on the arctangent function, the surface reflectance spectral modeling is carried out. The root mean square error of the measured and simulated spectra of each site is within 0.6%, and the correlation coefficient is above 0.99. The results show that the four-parameter spectral model can accurately describe the reflectance spectra of desert sites. The surface reflectance calculated by the model is used to calibrate the FY-3D medium resolution spectral imager (MERSI) site instead of the measured surface reflectance, it is found that compared with the results calculated based on the measured spectra, the relative deviation of each band of MERSI obtained by the model is less than 3%, indicating that the desert four-parameter reflectance spectral model can be well applied to the calibration of MERSI.