Abstract: Chang-6 oil layer of Triassic Yanchang formation in Xunyi area of Ordos basin is a typical low porosity and low permeability reservoir and the lithology is mainly feldspathic lithic sandstone and lithic feldspathic sandstone.The pore type is mainly residual intergranular and feldspar dissolution porosity.The pore throat portfolios are mainly fine pores and pore throat fine throat,reservoir heterogeneity is strong.Reservoir properties are mainly affected by the combined effect of rock composition,sedimentary facies,pore structure and diagenesis.Chang6 oil reservoir can be divided into classⅠ,Ⅱ,Ⅲ,Ⅳtype.Through a comprehensive evaluation,the reservoir mainly belongs toⅠandⅡtypes.