The Northern Qili and Longmen gas fields, with proven reserves of 6316×108 m3 and great exploration potential, have been discovered the recent exploration of the Lower Triassic Feixianguan Formation around Kaijiang- Liangping trough in Sichuan basin, Puguang. The reservoir interval is mainly composed of dolomites from oolitic shoal. To explore the regional dolomitization and its control over the reservoir development, this paper analyzes the types, distribution, formation mechanism of dolomites and the pore evolution of the dolomite reservoirs in the study area based on thin section observations, well- tie correlation combined with cathodoluminescence, in- situ LA- ICP- MS major and trace elements strontium isotope and fluid inclusion analyses. The rock types of the second member of the Feixianguan Formation in the Dazhu- Kaijiang area of eastern Sichuan basin mainly include micritic limestone, grainstone and dolomite which mainly includes residual granular dolomite and crystalline dolomite, and transitional rocks such as dolomitic granular limestone are also common. The development and distribution of granular limestone and dolomite are mainly controlled by sedimentary facies. In the interval from the late stage of the first member of the Feixianguan deposition to the early stage of the second member, the southwest region of the study area like Shapingchang structure was an open platform facies deposit, and the oolitic shoals are sporadic, the degree of dolomitization is also weak. With the progradation and aggradation of the oolitic shoals in the middle to late stage of the second member of the Feixianguan Formation, a restricted environment is formed between or behind the oolitic shoals. As a result, the degree of dolomitization in the oolitic shoals in the Shuangjiaba- Longmen structure is enhanced, forming a widely distributed and thickly deposited dolomite area. The dolomites in the study area mainly show dull- red or non- luminance cathodoluminescence under cathode rays, and are the products of high salinity brine by infiltration and circumfluence in contemporaneous and penecontemporaneous period. The dolomitization fluid was mainly seawater at the time for the Feixianguan deposition. However, the dolomitization fluid of the dolomite that formed in a restricted environment is a mixture of meteoric freshwater and dominantly seawater. The Mg 2+ is mainly provided by lime lagoon formed by the aggradation of the oolitic shoals in the early stage of the second member of the Feixianguan Formation, and by the lime lagoon and dolomitic lagoon formed by the progradation and aggradation of the oolitic shoals in the middle to the late stage of the second member of the Feixianguan Formation. The main reservoir spaces in reservoir rocks of the second member of the Feixianguan Formation in the study area are intergranular pores, mould pores and intergranular pores, and fractures are not developed. A combination of diagenetic sequence, pore evolution and fluid inclusion analysis shows great consistency between pore abundance and dolomite distribution. As compaction resistance increases, intercrystalline pores in dolomite accommodate hydrocarbon charging, providing a good base for reservoir development. Liquid and gaseous hydrocarbon are identified in the reservoir rocks from the second member of the Feixianguan Formation, indicating there are at least two stages of hydrocarbon accumulation, and pore development and hydrocarbon charging also have a good coupling relationship.