The traditional reservoir operation mainly meet the demand of water supply and flood control, while the purpose of the reservoir operation based on 3E decision realized economically, socially and ecologically multi-objective reservoir optimal operation achieving . First, the monthly minimum and frequency calculation methods were used to calculate the minimum and the optimal ecological flows, and the best ecological flow suitable for Kongtong reservoir was selected; then, a 3E model was established, the weights of different goals were determined using the binary comparison of fuzzy decision analysis method to simplify multi-objectives; Finally, the model was solved using the particle swarm optimization algorithm. The results showed that: the reservoir water supply which had the maximum benefit was 46.22 million m3, of which the agricultural total water supply was 36.3 million m3, total industrial and domestic water supply was 9.92 million m3, while the ecological water utilization for maintaining ecological base flow was 23.11 million m3. This not only provides the basis for decision of the reservoir in the future operation, but also propses suggestions of strengthen water conservancy for solving the contradiction of water reservoir.