The mineralogy of three soils, derived from red sandstone, purple sandstone and red-purple sandstone was studied by XRD, IR, TEM and XRF. Results showed that total chemical composition of these three soils varied greatly, especially for Fe, Ti, Mn and basic elements, which demonstrated that these three parent rocks were formed in different sedimentary environments. It was found that soil derived from red sandstone was mainly composed of disorder kaolinite and halloysite, and some illite and vermiculite, derived from purple sandstone mainly illite, and some halloysite and montmolinite. Meanwhile montmolinite and hematite were the major minerals in soil from red-purple sandstone. The iron oxide minerals of these soils were also varied greatly, no-Al substituted hematite was the only crystalline Fe oxide in soil from purple sandstone and redpurple sandstone; whereas the coexistent goethite and hematite is nearly amount in soil from red sandstone, and Al-substituted amounts of these iron oxides were 16.6 and 2.1 mole % respectively. Difference in types and amount of iron oxides resulted in different colors of these soils.