Infrared spectroscopy has been applied in soil analysis as a new method for years, and various infrared techniques have been identified with regard to the wavelength and signal detector. The infrared spectra of loess soil were characterized using infrared photoacoustic and reflectance spectroscopy in near- and mid-infrared region, and more closely relationship were found between the absorptions and soil attributes in mid-infrared region, which benefited the soil quantitative and qualitative analyses. The characteristics of infrared reflectance spectra significantly differed from infrared photoacoustic spectra; in mid-infrared region, there were counterpart absorptions in reflectance and photoacoustic spectra, but the relative intensity of absorption bands were significantly different, and the locations of some bands shifted, especially in the wave-number range of 1 000-2 000 cm-1. In the classification of loess, reflectance spectroscopy seemed better than photoacoutic spectroscopy. In conclusion, the sensibilities of infrared reflectance and photoacoustic spectroscopy in different wavelength varied, and infrared photoacoutic spectroscopy indicated unique advantage in the quantitative and qualitative analysis for opaque and heterogeneous soil samples.