After decades of exploration, geologists have obtained 100 billion cubic meters of proven reserves in Gaoshiti—Moxi area of Sichuan Basin. In order to study the characteristics of dolomite reservoir and the main controlling factors of reservoir formation in the Dengying Formation, Sinian System（≈Ediacaran System), in Gaoshiti—Moxi area, Sichuan Basin. Methods: Core observation, thin section identification, cathodoluminescence analysis, physical property test, scanning electron microscopy observation, main trace elements and carbon and oxygen isotope analysis, inclusion homogenization temperature test, sedimentary facies zone division, analysis on the controlling effect of macrostructure on oil and gas accumulation, etc. Results: The results show that:①There are high quality dolostone reservoirs in the 4th Member of the Dengying Formation in Gaoshiti—Moxi area, including mudstone algal dolostone, arenaceous dolostone and crystalline dolostone.②The high- quality reservoirs in the 4th Member of the Dengying Formation were subjected to the atmospheric fresh water karstification of Tongwan Episode II and the hydrothermal transformation during burial period. The dissolution pore was widely developed with an average porosity of 4. 8% and an average permeability of 0. 5×10-3μm2, which was a “low- porosity—ultra- low- permeability” reservoir.③The favorable facies zone and dolomitization control the development and distribution of high- quality reservoirs, which are mostly distributed in the platform margin zone at the edge of the rift trough, especially in the algae- hill- beach facies dolomite, which is the main gas- producing layer in the study area. The hydrothermal dolomitization during burial period improves the reservoir physical properties and pore structure. It can be seen that the saddle dolomite filled with various hydrothermal minerals, dissolution pores and cracks has typical fog core bright edge structure, negative oxygen isotope composition, average homogenization temperature of fluid inclusions as high as 175. 7 ℃, bright red light with high Mn content and cathodoluminescence. Conclusions: The research results have important theoretical significance for expanding oil and gas exploration in ancient carbonate rocks.