Abstract: The growth of current macro economic is slow， and the weights of economic value added （EVA） and asset-liability ratio has become more and more lager in the enterprise performance evaluation of SASAC， so the investment scale of power grid company further reduces. The strategic goal of power grid company is the pursuit of economic benefits in the precondition of realizing social responsibility， so the investment scale model has very important significance for the rationality of investment decisions of power grid company. Taking Chongqing Power Supply Company as the research object， a systematic method of combined qualitative and quantitative was used to select index and the index system of investment scale was established for power supply company. The index weight was determined by using analytic hierarchy process （AHP） method， then the comprehensive evaluation of power supply company was carried out， finally the investment scale model of power supply company was built according to the relationship between the comprehensive evaluation and investment scale of subsidiary. The investment scale model can be theoretical basis for the investment allocation decisions of power grid company， realizing the comprehensive， balanced and sustainable development of power grid enterprises， as well as promoting the healthy and steadily improvement of enterprise development.

Key words: power supply company, index system, comprehensive evaluation, investment scale model