Abstract: Through core observation,thin section identification,scanning electron microscope,image size,image analytical means such as pore and high pressure mercury,the research on Chang-8 reservoir characteristics and influential factors of physical property in Zhengning-Yijun area has been carried out.Studies have shown that the main types of Chang-8 reservoir are fine-very fine-grained feldspar lithic sandstone and lithic arkose,with carbonate cements as the center.The pore types are mainly intergranular pore and feldspar dissolved pore.Chang-8 reservoirs belong to shallow water lake delta type of tight sandstone oil reservoir.Affected by sedimentation,diagenesis and pore structure factors,Chang-8 reservoirs are believed to be of high content of feldspar particles,carbonate cement content and poor pore structure,which are the main causes of low permeability reservoirs.The influential factors analysis of physical property can provide strong support for Chang-8 reservoir densification studies.