Abstract:Based on study of thin-section analysis, \"X\" diffraction and scanning electricity microscopy observation analysis, the basic characteristics of the main layers of clay minerals has been sysernatically reserched in eastern Ordos Basin.It is indicated that the characteristics of clay mineral is affect by source rock, sedimentary facies and diagenesis. The controlling factors of clay minerals of different layers were different.Such as, in the 5th section of Shiqingfeng formation and the 8th section of Shihezi formation, controlling factors are source rock and sedimentary facies, but in the 2th section of Shanxi formation and Taiyuan formation, diagenesis and depositional facies influence are impotrant. To strengthen the study on the characteristics of clay minerals of different layers, the potential sensitivity of main reservoircan be clearly maked out, and this preliminary conclusion may play certain reference significance to the protection and renovation of reservoir.