The invention relates to an electric power system parameter identification method based on the robust estimation and the Lagrange multiplier method, and belongs to the technical field of electric power system dispatching automation and power grid emulation. The electric power system parameter identification method of the robust estimation and the Lagrange multiplier method is provided. The method includes the steps of acquiring initial sub-circuit parameter values and a measurement value of an electric power system, using a robust estimation model based on maximum cross entropy criteria to perform solution, and calculating a regularized Lagrange multiplier of each sub-circuit parameter according to a robust estimation result, wherein the sub-circuit parameters with larger regularized Lagrange multipliers possibly may also be wrong. Compared with a traditional electric power system parameter identification method, the electric power system parameter identification method based on the robust estimation and the Lagrange multiplier method has the advantages that poor-measurement influences on a parameter identification result are eliminated by the utilization of the robust estimation model, the Lagrange multiplier method is used to achieve identification on the suspicious electric power system sub-circuit parameters, and better identification precision and robustness are achieved.