Abstract: The low resistivity reservoirs are well developed in Enping Sag, and it is difficult to identify the fluid properties of these low resistivity reservoirs because the reservoir rocks are fine in particles, with high mud content, and the structural height is low. Due to the influence of mud content, Indonesia formula is used to calculate water saturation and eliminate influence of mud content. Irreducible water saturation is determined by using the relationship between porosity, permeability and irreducible water saturation. Then the relative permeability can be figured out through the relationship between relative permeability and water saturation, irreducible water saturation. Based on these accurate parameters, the water cut can be calculated by making use of the logging data, and then the property of reservoir fluid is determined according to the water cut. The practical application shows that it is a better way to distinguish the low resistivity reservoir and determine its fluid properties.