Abstract: Nanshanping ancient reservoir is the typical representative of Southern China's Upper Sinian Dengying formation in dolomite reservoir. Based on the field profiles analysis and observation under microscope of the asphalt residue on the reservoir and within reservoir, the reservoir characteristics and diagenesis evolution process is studied. According to the reservoir mineral composition and pore formation and evolution, the reservoir evolution process is divided into six stages as deposition phase, the first shallow phase, supergene stage, the second shallow stage, deep buried stage and tectonic movement stage. Nanshanping Dengying formation reservoir is the platform edge shallow and inter-bank deposition, the fine powder crystal dolomite, micritic dolomite, oolitic dolomite formed in the deposition is the material basis of late diagenetic reformation. Dolomitization and supergene karstification is the main constructive diagenesis, which formed the main space for oil and gas storage.