Bymeans of casting thin sections and part of the ordinary thin sections and combined with scanning electronic microscope, cathodeluminescence and claymineral X-ray diffraction analysis method, the diagenesis, diagenetic sequence of the third member of Shahejie Formation in Banqiao Sag were analyzed. The result shows that diagenesis is mainly of cementation, metasomatism and dissolution. On the basis of the evolution of organic matter and clay minerals, the diagenetic stage ofBanqiao Sag is divided, and Sha 3 member is mainly in middle diagenetic Aand B stage. Dissolution is constructive for reservoir properties. Throughmulti-factor analysis, the comprehensive reservoir evaluation was carried out, which provides foundation for the deep oil and gas exploration.