Abstract: This article uses the DC power flow method to first construct the grid elastic potential energy transfer coefficient. The grid elastic potential energy coefficient quantitatively reflects the different impacts of different lines on the safety of the power grid, and can therefore be used to identify key lines in the power grid. After identifying the critical lines, it is necessary to minimize the impact of the critical lines on the power grid. Therefore, a flexible potential energy expression for the N-1 post-mapping of the power grid is proposed. This allows for quick determination of whether the optimization has been successful by only knowing the active power and line parameters of the lines before the N-1 of the power grid, greatly improving the speed of judgment without the need to separately perform power flow calculations on different lines of the power grid before N-1 and then make a judgment.