The inner oil field of Daqing Changyuan has entered a period of high water cut. The water drive development object has gradually changed from medium and high permeable layer to poor thin reservoir. Therefore, the law of water drive development also has the big difference. And the characteristic of oil–water infiltrating fluid has changed. Therefore, taking the demonstration area in X block as an example, it is found that there is a certain relationship between the ratio of water–oil relative permeability and the normalized water saturation, and the relationship is still valid in the high water cut stage. By compounding the normalized curves of single layer, the composite relative permeability curves of multiple layers are obtained. Based on the composite phase permeability curves, a new water cut prediction model based on composite phase permeability is established. The result of research shows that the new model is more accurate. The average error of the method for predicting water cut is 0.24%. Compared with the method of water drive curves, the calculation precision is improved by 1.79%. When using the prediction model based on composite phase permeability, considering the relationship of water–oil ratio, the prediction accuracy is higher, which is beneficial to guide the oil field development planning.