In order to open up a vast range of prospects for oil and gas exploration and development in Zhenjing area, southern Ordos Basin, series of research methods such as rock thin sections, cast sections, scanning electron microscope and mercury penetration of constant speed are used to analyze core hole data for surveying fair reservoirs. The result shows that feldspar lithic sandstone and lithic feldspar sandstone are the main reservoir lithologies, with low compositional maturity and low textural maturity, the main reservoir spaces are intergranular pores and dissolved pores, and the reservoir is characterized by poor-middle property, poor original productivity and strong heterogeneity. Combined with production performance, the evaluation parameters for lowpermeability reservoir such as throat radius, percentage of mobile fluid, start-up pressure gradient and active porosity are selected to evaluate Chang 81 reservoir. According to the result, Chang 81 reservoir can be divided into three types. The typeⅠis better reservoir, type Ⅱ is medium reservoir, and type Ⅲ is poor reservoir. The typeⅡand type Ⅲ are the main reservoir in the study area, while typeⅠis seldom.