Weight calculation plays an important role in river health assessment. There are two main classes of methods for determining index weights: subjective weight-assignment methods and objective weightassignment methods. Both types of methods have their own advantages and disadvantages. Subjective weight-assignment methods reflect the intention of decision makers with certain subjectivity. Objective weight-assignment methods mainly rely on complete mathematical theories and methods and tend to ignore the subjective information of the decision makers; thus, they do not consider the differences among index. Both methods have deficiencies. To make the calculation of index weights more rational, this study introduces a combined weight-assignment idea based on game theory. This method combines a subjective weight-assignment method (analytic hierarchy process) with an objective weight-assignment method (entropy method) to calculate the weight, which avoids the subjectivity of subjective weightassignment methods and the absolute objectivity of the objective weight-assignment methods. The Luanhe River in the Haihe River Basin was selected as the study area, and the weight of the health evaluation index system of the Luanhe River was calculated using the combined weight-assignment method to assess the degree of influence of each index on river health. The research shows that using this method to calculate the weight has important practical applications for river health assessment.