The Middle Permian Maokou Formation is an important stratigraphic series for increasing reserves and production in Sichuan Basin.The preliminary exploration mainly focused on the limestone fissure type reservoirs related to the weathered crust at the top of the Maokou Formation.In recent years,with the breakthrough of a series of high-yield wells in the central Sichuan region,the significant exploration potential in dolomite of the Maokou Member 2 has been demonstrated,including the intraplatform shoal dolomite reservoir of the lower member of Permian Maokou Member 2 in Hechuan-Tongnan area,while the strong reservoir heterogeneity restricts the further exploration.Based on core and thin section observation,physical property experiments and geochemical analysis,the basic characteristics of dolomite reservoir of the lower submember of Maokou Member 2 in Hechuan-Tongnan area are systematically analyzed,and the genesis and formation mechanism of dolomite reservoir are discussed.The results show that the dolomite reservoir of lower submember of Maokou Member 2 consists of pinhole dolomite and vuggy dolomite,and the reservoir space is characterized by intercrystal(dissolved)pore,karst cave and fracture as the main seepage channel.The reservoir type is mainly fracture-vuggy reservoir,and secondly fracture-pore reservoir.The average porosity and permeability of pinhole dolomite of the full diameter sample are 2.50，and 0.806×10-3 μm2,and these of vuggy dolomite are 4.32，and 1.047×10-3 μm2.Combined with previous sedimentation and diagenesis research,it is considered that the high energy shoal facies is material base for reservoir development and multi-stage karstification is the key for the formation of high quality reservoir.Penecontemporaneous dolomitization is the key to reservoir space preservation by enhancing the compaction resistance of rocks.The late hydrothermal dolomitization of Maokou Formation related with the Dongwu Movement(Emei taphrogenesis in the upper-Yangtze region)in the late Middle Permian is dominated by cementing and filling early pores,which reduces the reservoir performance of dolomite.This study provides a basis for predicting the distribution zone of high-quality reservoirs in Maokou Formation.