Abstract: Demand side management has attracted wider and wider attention under the electric power system reform because it conforms to the development tendency of the smart grid. In this paper, the cost indexes and benefit indexes of demand side management are determined to evaluate their impacts on the power grid companies under the power transmission and distribution price reform. It is divided into short-term and long-term pricing according to the different forms of the transmission and distribution price. Then short-term and long-term cost-benefit evaluation models are built according to the different accounting methods of total revenue. Being applicable to a variety of demand side management strategies, such variables as ‘avoidable peak load capacity’ and ‘increased transmission and distribution energy’ are set in the model. The three-dimensional results of short-term and long-term evaluation together with the change trend of the transmission and distribution price for a regional grid are obtained from case analysis, which validates the objectivity and effectiveness of the evaluation model.