Based upon detailed research on the bioclastic limestones of Moukou formation in southern Sichuan basin, a scheme of classification is proposed. And their stages of diagenetic changes were also analyzed. The character of reservoir voids in the bioclastic limestones is roughly discussed, which emphasized the affect of various lithologic factors on the reservoir property. Finally, the reservoir regularity of gas in this limestone is stated as follows.(1) Intercrystal pore of sparry calcite and dolomite behaved as the main reservoir space. The cavern of the karst system and adjacent pore may be regarded as enriched space, maintaining the stability of production. It was realized that fracture fissures were the main background of high gas production.(2) The sparitic red algal limestone and dolomitic echinodermatic limestone play an important role in reservoir capacity, while the micritic shelly green algal limestone and shelly marlite are the main resource rocks. Obviously, the organism, especially the algae, is the chief factor in the formation of oil-gas reservoir.(3) Bed algal bans occurred in uplifted plarform margin is the main reservoir facies, which appear to be more promising in the reservoir behavior, especially those occured near the margin of open sea. And the semi-closed lagoon within subsidence basin is found to be the main resource facies with favourable lithological character on the side of green algal bank. Hence, the transitional belt between the uplifted platform and the subsidence basin is considered as the most available facies zone for gas exploration.(4) In general, the recrystallization, karst development and dolomization can improve the reservoir capacity of strata, while the existence of muddy constituents may reduce the reservoir capability. During the period after the sedimentation of Moukou formation and before the sedimentation of Leping formation, there occurred an epeirogenetic uplift, accompanying the development of paleokarst.(5) Bioclastic limestone of Moukou formation is overlain by Leping coal-series, the oil (gas) originated in the Lower part and reserved in its upper part. Thus a self-generate and self-reserving gas-containing formation with large reservoir and production capacity were formed.