In order to find the variation law of soil spectral characteristics and their relationship with vegetation cover change, the author took the Minqin County in the lower reaches of Shiyang River as objective, SVC HR768 type ground object spectrometer was used to measure the soil spectrum of sandy land, gravel gobi and soil gobi. Based on characteristic curve of soil spectral reflectance and first derivative analysis, the result showed that the soils in study area had the unique wave-shaped spectral curves; the spectra were similar in shape. Spectral reflectance of clay gobi was significantly higher than the sandy land and gravel gobi, and it was most obvious in 700-1000 nm. In the red edge range (680-760 nm), derivative spectra could inhibit soil background information, highlight the ‘red edge’ effect of vegetation, this wavelength could be used in quantitative inversion of desert vegetation. In the measured wavelength range, with the increasing of vegetation cover, the soil spectral reflectance of sandy land and gravel gobi was reducing. Soil reflectance was sensitive to vegetation changes. So, desert soil spectral reflectance curve could reflect the change of desertification degree, it could be used as a reliable basis for quantitative studies of desertification.