The invention discloses an electric power flow planning optimization method. The method comprises the following steps: establishing an uncertainty set of new energy output according to historical data; establishing a power flow planning optimization model by taking minimization of social total cost as a target; and solving the model, and outputting an optimal solution. According to the method, uncertainty of output of new energy such as wind power and photovoltaic power in actual planning operation of a power grid is considered, a model for optimizing power flow planning is established to solve an optimal solution by taking minimization of social total cost as a target according to an interval of the output of the new energy, and the power flow is effectively planned while the cost is saved.