Abstract: To supply scientific and valid foundation of exploitation,we study the physical property and influence elements of Chang 6 Bed of Yanchang Formation in Baliangou-Jinzhuang area of Nanniwan Oil Field.A synthesis analysis by using the casting lamella,scanning electron microscope,porosity and permeability analysis,the log interpretation and mercury injection test was carried out.The results show that the lithologic characteristics of reservoir mainly include silty-midium arkose.The pore space of the reservoir mainly includes the dissolution and residual intergranular pores.Pore structures are mostly the type of middle class of discharge pressure and throat and the type of high class of discharge pressure and thin throat,with strong variability,complexity and heterogeneity.General property belongs to low hole extra-low permeability reservoirs.The characteristics of the reservoir are affected by deposition and diagenesis,and underwater distributary channel is the main favorable microfacie.The physical property was declined mainly for the cementation and compaction and pressolution processes.The dissolution is intense,whose dissolution pore is the important pore space for Chang 6 sandstone reservoir in the study region.The microfracture developed here has constructive effect on improving the petrophysical property of the reservoir and connectivity of pore throat.