The invention discloses a power dispatching method and system. The method comprises the steps of performing calculation based on collected power generation capacity, user reduced load and energy output data of a power generation company and a pre-built dispatching model to obtain the minimum cost of power generation; and obtaining an optimal generator set combination scheme according to the minimum cost, wherein the dispatching model is built according to the power generation cost, the demand response aggregator cost and the load reduction cost of a generator set and the energy abandoning cost. According to the technical scheme provided by the method and the system, a dispatching problem between the generator set and a demand response is provided; efficient operation and benign operation of the power market are facilitated; the social and environmental benefits generated by electric energy are increased; and due to the participation of the demand response, the pressure of the generatorset, power grid dispatching and power transmission in a load peak period is reduced, the avoidable capacity cost and the avoidable electric capacity cost of the power system are reduced, the operation proportion of a peak shaving unit is reduced, and the fixed investment of the whole power system is reduced, so that the power resources can be more efficiently utilized.