Abstract: The equilibrium solution of a non-inferior solution set for a multi-objective decision-making model is not unique when the set is non-convex. To solve this problem, this study develops an ideal mean rate method (IMRM) combining a technique of order preference by similarity to an ideal solution (TOPSIS), and the mean rate method (MRM). The existence and uniqueness of the optimal equilibrium solution of IMRM are proved. We analyze and compare the solutions of MRM, TOPSIS and IMRM to the multi-objective scheduling decision problem in the Jinguan power group at the Yalong River. Results show that IMRM can not only achieve the best solution that satisfies the multi-objective scheduling, but offer a qualitative and quantitative description of the relationship among the objectives of flood control, power generation, and ecological protection. The theory of IMRM is proved to be complete, and it is more likely to be accepted by decision makers.