The reservoir ofXishanyao Formation in Niuquanhu Oilfield is characterized by lowporosity, lowpermeability and lowpressure. Because the injection water is fresh water and the original oil saturation is low, the resistivity of water flooded layer is high. The water flooded layers are often wrongly interpreted as oil layers by using conventional log interpretation, which results in high water cut after the perforating operation. The conventional logging data combining with oil testing data and core analysis are applied to study the geophysical characteristics and quantitative interpretation model of water flooded layers, and establish the interpretation method for water flooded layer in Niuquanhu Oilfield. The field application proves the good effect.