Based on their connotation and classification, an evaluation index system for the functions of a river is developed considering its natural function, ecological function, social function and disastrous characteristics. On this basis, the AHP and the improved entropy method are employed to respectively determine the objective and subjective weights of various indices, and the comprehensive weights are then determined through linear combination. The improved grey hierarchical model is thus established. The evaluation index system for comprehensive functions of rivers and the improved grey hierarchical model are applied to the evaluation of functions of Baitiao River. The results show that the comprehensive functions of Baitiao River are very good and agree with the actual situations. The proposed grey hierarchical model can integrate the subjective and objective weight information and fully consider the relationship among various indices, and it is of great reliability and practicability.