Characterization of three source clay minerals, illite, kaolin and montmorillonite, were made using three mid-infrared spectroscopic techniques (attenuated total reflectance (FTIR-ATR), transmittance spectroscopy, and photoacoustic spectroscopy (FTIR-PAS)). For the FTIR transmittance spectra, there are three main absorption regions: 3000～3800cm-1,1300～1800cm-1, and 500～1200cm-1, and sharp differences can be found in each region. For the FTIR-ATR spectra, there are absorptions with main difference in the region of 800～1200cm-1. For the FTIR-PAS spectra, there are also three similar absorption regions as FTIR transmittance spectra. However more information is found in the FTIR-PAS spectra comparing with FTIR transmittance absorptions. The FTIR-PAS was applied to identify three soil types and the results revealed that: Hailun soil was characterized as montmorillonite type soil with medium calcium carbonate content, Changwu soil was characterized as montmorillonite/illite type soil with high calcium carbonate content, and Qiyang soil was characterized as kaolin type soil with low calcium carbonate content