The Cretaceous Mishrif Formation in the southeastern Iraq was deposited in a carbonate ramp environment, characterized by diverse and complex reservoir origins and significant development contradictions. Based on data of 11 coring wells across four oilfields in the southeastern Iraq, the sedimentary characteristics of the carbonate ramp were clarified, reservoir types were classified by integrating pore genesis, composition, physical properties, microstructure, and production performance, and the controlling mechanisms of the carbonate ramp on reservoir development were identified. The results show that the carbonate ramp of the Mishrif Formation is mainly influenced by wave action with weak tidal activity. Facies variation is not pronounced, components are poorly differentiated, reefs are difficult to preserve, and bioclastic shoals are widely developed. Allochems are rare but bioclasts are abundant. Gravity flows are absent, and lithologies are diverse in restricted environments. Reservoirs are classified into four types:vug-dominated, intergranular pore-dominated, isolated pore-dominated, and microporous-dominated. Vug-dominated reservoirs develop in point shoals and are jointly controlled by sedimentation, penecontemporaneous diagenesis, and tectonics. Intergranular pore-dominated reservoirs occur in barrier shoals and tidal channels, mainly controlled by sedimentation. Isolated pore-dominated reservoir form in lagoons and front shoal-basin settings, controlled by diagenesis. Microporous-dominated reservoirs develop in low-energy settings such as lagoons, slope bottoms, and deep-water shelves, with limited diagenetic alteration. Overall, in carbonate ramps, high-energy sedimentation promotes the development of high-quality reservoirs with strong microstructure heterogeneity. Deep-water and restricted environments control the formation of baffles and barriers. A large number of high-porosity but low-permeability reservoirs occur in open and deep-water environments, showing weak lateral heterogeneity, while restricted environments host complex reservoir combinations, with strong spatial heterogeneity due to facies changes.