At present, the domestic reform of the electric power system is comprehensively deepening, and the power retail business will be liberalized on a large scale, which will have a huge impact on the production and operation of power grid enterprises while bringing dividends to the society. The system dynamics model is introduced to conduct quantitative research. According to the business process, seven submodels of power retail business costrevenue model, power transmission and distribution business revenuscost model, power valueadded service revenuscost model, grid staff turnover model, cash flow model, demandside response model, power retail and related business profit model are respectively established. Based on the relevant data of the 2018 annual report of the electric power market in a province, the influence of the relevant indicators of the electric power grid is analyzed through three scenarios, namely the change of the growth rate of marketized electric power, the change of the agent electric power of the electric power selling company and the change of the price difference between the purchase and sale of electric power. The study has certain reference value for power grid enterprises to actively respond to the reform and carry out the evaluation of power system reform.