A optimal dispatching model for the hydropower stations is established

in which two objective functions including maximizing peaking capacity benefit and maximizing power generation are involved

and the improved particle swarm optimization（PSO） algorithm solving the model is proposed.The algorithm can handle the level multi-objective optimization problem effectively

and has the advantages of good convergence property and simplicity.Optimal dispatching problem of the Three Gorges Cascade Hydropower System during low-flow period is studied with the algorithm to obtain the maximum peaking capacity benefit.