The invention relates to a power grid investment planning budget system based on system dynamics. The system comprises an electric quantity demand module, an investment planning decision module, a power transmission and distribution price module and a power grid profit module. The electric quantity demand module predicts a future electric quantity demand of a power grid. Te investment planning decision module predicts future planned investment and actual investment of the power grid. The power transmission and distribution price module determines the annual asset increment of a future power grid, predicts the power transmission and distribution price and determines the profit of power transmission and distribution. The power grid profit module measures and calculates the guarantee profit and the electricity selling profit of the power grid to obtain the total profit of the power grid. The system can comprehensively consider the incidence relation among the electric quantity demand, theinvestment plan, the power grid profit and the investment capability in the power transmission and distribution price reform environment.