Abstract: By using experimental testing techniques such as core observation,rock slices identification,scanning electron microscopy and pressure mercury test,the characteristics and heterogeneity in Yan'an reservoir was studied.The results indicate the rock types of the Yan 9 member are mainly gray,gray-green,gray-brown feldspar lithic quartz sandstone,the sorting of sandstone is medium-good,roundness is mostly round,secondary edge-sub-round.Particles are between the line,pointline contact,point contact and bump contact can be partially seen,mostly for particle support.From the capillary pressure curve,it can be seen:the pore type of Yan 9 is medium hole-throat type,medium and small hole type.The reservoir types in Yan'an formation include the following four types,namely intergranular dissolution,intergranular dissolution,residual intergranular pores and casting holes.Among them,79.23% of the intergranular pores are the largest,0.63% of the casting holes is the least.The reservoir of Yan 9 member belongs to medium porosity,medium-low permeability reservoirs,and the reservoirs have good physical properties.