Grid investment optimization is an effective method for solving the mismatch between investment demand and the investment capacity of power grids. China is carrying out a new round of power system reform, and the main content is to control the revenue of the power grid enterprise through the transmission and distribution tariff policy. Revenue control may make the investment capacity of the power grid enterprise appear even more insufficient than it is currently. This paper studies the influence of the transmission and distribution tariff policy on the cash flow of the power grid enterprise and establishes an investment optimization decision-making model for the corporation using system dynamics theory. Then, taking a city as an example to undertake an empirical analysis, the paper puts forward suggestions and policy implications for the investment decision of the power grid enterprise after the reform of the electricity market.