The formation and distribution of high quality reservoirs are key to the prospecting in deep marine carbonates. In recent years, the discoveries in (ultra-) deep-buried carbonate reservoirs of the giant Puguang gas field and many others have broken through the early viewpoints. The formation mechanism of this kind of reservoirs under the limited conditions has become the highlight, as well as the nodus of researches. Based on the petrological characteristics from drilling cores and thinsections, and data from porosities, permeabilities, and isotopes, three controlling factors are summarized: (1) the early depositional and diagenetic environment which controlled the early porosities; (2) tectonics and formation pressures which formed the fractures and dissolutions; and (3) fluid-rock interactions that influenced the deep burial dissolution and the preservation of the porosities.