The invention discloses a theoretical model establishing method for predicting the development investment capacity of a power grid. The method comprises: on the basis of the existing cash flow, dividing the investment scale into an operation activity cash flow, an investment activity cash flow and a financing activity cash flow, establishing an investment capability theoretical model, a target function CapEx = f(X, p, H), wherein CapEx is the investment scale, X is a related variable, p is a parameter, H is a key hypothesis, TP is the total profit, DR is the debt-to-assets ratio. The method has the advantages that a scientific and reasonable prediction model is constructed, a scientific basis is provided for investment decisions of power grid companies, and the method is of great significance to improvement of lean management and control of the companies.