Dongying depression is one of the most prolific hydrocarbon areas in China. The Paleogene stratum consists of underwater fan, littoral-shallow lacustrine and delta facies sandstones. Diagenesis and pore evolution have exerted great effects on the proporties of reservoir rocks. The study performed by the authors is of significance in finding favorable reservoir zones in Dongying depression. Many thin sections were analyzed by such means as standard petrographic microscope, X-ray diffraction and scanning electron microscope analysis so as to study the selected samples. Diagenetic complexity shows that compaction and cementation lead to decrease in porosity, whereas solution of unsteady minerals and carbonate cements result in increase in porosity. The evolution of organic materials and the sequence of clay minerals suggest that the diagenesis and the pore evolution of the sandstone in different structural belts varied obviously with the increase of the buried depth, and the reservoirs might be classified into three pore evolution zones, namely, the primary shallow pore zone, the primarysecondary transitional pore zone, and the secondary deep pore zone. The sandstones serve as well-developed secondary pore zones.