In recent years，a large number of low resistivity oil reservoirs have been discovered in Chang4+5 member of Yanchang Formation of Jiyuan area，Ordos Basin. But there are many theoretical and technical problems in the genetic mechanism and identification methods，which often results in misidentification or loss of oil reservoirs in the study area. To study the genetic mechanism and identification methods of low resistivity oil reservoirs in Chang4+5 member of Yanchang Formation in Jiyuan area，a series of measurements and analysis such as core and thin section observation，SEM observation，XRD and mercury injection tests etc.，combining with data of logging，oil testing and production，were used. The result shows that low amplitude structure，complex relationship between oil and water，high immobile water saturation and high formation water salinity are the main causes of low resistivity oil reservoirs in Chang4+5 member. Among which，the high immobile water saturation in the study area is controlled by fine particle size，high clay content and complex pore structure.The case study shows that three methods of identifying low resistivity oil reservoirs were proposed in this paper：a qualitative contrast method of identifying reservoirs adjacent to low resistivity oil reservoirs；a quantitative identification method of analyzing mobile water of low resistivity oil reservoirs based on a three dimensional model of the relationship among clay content，ratio of porosity to permeability and immobile water saturation；and a crossplot method of identifying low resistivity oil reservoirs fast and accurately. These methods can improve the coincidence rate between the nterpretation results and the oil test results.