Abstract: The tight sandstone reservoir of 2nd member of Xjiahe famation is the main gas producing formation in Yuanba area.Based on the analysis of core,casting thin sections and mercury injection data,the studies on reservoir petrology characteristics,physical characteristics,reservoir space and the influential factors analysis of reservoir development have been carried out.The results show the reservoir is dense while the physical properties are poor.The reservoirs are mainly affected by tectonism,sedimentation,diagenesis and dissolution.There is a strong gas production potential where the tectonic movement is intense.The onshore part is easier to form a high quality reservoir than that of underwater.Diagenesis is mainly for damage to physical properties.Dissolution mainly produces secondary pores and it can improve the reservoir permeability reservoir performance.