Abstract: By using core observation,thin section identification and various testing data,a systematic study on reservoir microscopic petrological characteristics and pore structure of western Sulige gas field has been carried out.The results show that reservoir sandstone from He-8 member and Shanxi formation is of higher cutting content and lower feldspar content.The rock type is mainly of lithic sandstone with low compositional maturity.Through diagenetic transformation,four kinds of pore types were mainly developed,including dissolved pore,inter-granular pore,inter-crystalline pore and micro-fractures.Among them,with larger aperture,the inter-granular pore and dissolved pore can provide occurrence space for hydrocarbon.Micro-fractures can effectively communicate reservoir and improve gas well capacity.The overall pore combination of the gas field is fine-micropore and fine-medium pore.As the main producing layer,the pore structure of the He-8 lower member and Shan-1 member is good,and it is good for hydrocarbon enrichment.