Abstract: The petroliferous diffence of the Lower Ordovician reservoir rocks in the eastern Or-dos Basin is resuIted from the non-uniformly geological conditions for the reservoir rocks,which is an interaction of paleo-elevation of the basement structure,and depression,lith-facies and paleogeography,diageneLsis and paleokarstification,among those factors,paleo-elevation of the basement and depression are the foundation,lithfacies is the geological condition,diagenesi is the key to geological process, and paleokarstification is a decisive factor.