Lowresistivity oil layer are widely developed in Wangji Oilfield. Due to the lowcontrast ratio of resistivity between oil layer and water layer, the log interpretation is difficult. Based on core test and formation water analysis, this paper analyzed the origin of low resistivity reservoir. The result shows that formation water salinity divergence, pore structure, thin bed development and drillingmud intrusion are the main influencing factors for lowresistivity of reservoir. This paper summarized three kinds of interpretation methods to identify the lowresistivity oil layer, namely oil and water layer identification in cross plot, induction electrolog and lateral logging united method and invading factor method. The actual practice shows that these interpretation methods are suitable for the identification and evaluation of lowresistivity reservoir.