The present takes the Qingyang, Gansu as an example, based on the mechanism of oil-gas microseepage, the spectra of the loess samples were measured, and the contents of carbonate minerals, clay minerals, Fe2+ and Fe3+, were analyzed. From their contents, it was shown that the carbonate mineralization and the red fading phenomenon are obvious for the known oil-gas field. Meanwhile, the parameters of absorption spectra of the loess samples were identified after the continuum was removed. The multiple regression analysis between the spectrum parameters (independent variables) and the mineral contents (the dependent variables) was implemented. The results indicate that the absorption depth is more sensitive. Thus, by their spectrum absorption parameters, 14 spectra of loess samples were clustered into two groups: samples in the known oil-gas field and unknown oil-gas field.