The reservoir characteristics and diagenesis of medium-deep Paleogene in Shinan slope area, Bozhong depression are studied by using thin sections observation, physical properties analysis, scanning electron microscope and X-ray diffraction analysis. It is showed that the reservoir sand is dominated by debris arkose and arkose arenite, with some mixed sediments of lacustrine carbonate and continental debris. Pore evolution and diagenesis are coupling with each other, and diagenesis evolution is the critical factor controlling reservoir development. Corrosion is the most important constructive diagenesis in the formation of high-quality reservoir in the medium-deep stratigraphy.