Abstract: Using the conventional core analysis data, such as the data of thin sections, scanning electron microscopy(SEM) and X-ray diffraction, the petrographic characteristics, diagenetic types, diagenetic stages and sequences as well as porosity evolution of the Paleogene sandstone reservoir in the Shenxian Depression are systematically studied. The results indicate that the lithology of Paleogene sandstone reservoir in the Shenxian Depression is primarily feldspathic lithic sandstone and lithic sandstone of low maturity. Compaction, cementation, dissolution and metasomatism are the main types of diagenesis influencing reservoir property in the study area. Based on the study of diagenetic stages and porosity evolution, the Paleogene sandstone reservoir in the study area is mainly remained in the stage B of early diagenesis upto the stage B of late diagenesis. The reservoir properties change drastically in different diagenetic stages.