Abstract: Using the theory of cooperative game,the problem of cost sharing in watershed water pollution abatement was transformed into a cost sharing game.On the basis of the traditional Shapley value method,a new but more universal concept of binomial semivalue solution was brought forth and adopted.The three adjacent administration regions in the Three-Gorge Reservoir on the Yangtze River were set as research objects and chemical oxygen demand (COD) as water quality index.The problem was solved with the multilinear extension method,taking into account its coalition structure.Results show that the solution satisfied the three conditions,i.e. super-additivity,individaual rationality and collective rationality,that a characteristic function of binomial semivalue must have,and that the cost of watershed water pollution abatement was fairly and reasonably allocated among the districts,which validates the effectiveness of this method.