Abstract: This paper studies the diagenesis of Upper Permian reefs in Tianfu area, Chongqing, Sichuan. Microcrystalization, interstitial sedimentation, cementation, dolomitization, silification, solution, neomorphism, compaction, pressure solution are formed in this area.Four diagenetic environments, i.e.the submarine, the meteoric phreatic and vadose, the shallow buried and deep buried, and epidiagesis environments are determined by the diagenetic features in the diagenetic history of reefs.The evolution of porosity isdiscussed by combing the diagenesis of carbonate rocks with the geological history of Sichuan Basin.