Abstract: Under the non-standard operating environment,the parameters of transmission lines and transformers will deviate from the normal standard values,especially the error of branch Impedance parameters related to leverage points,seriously affect the system’s accurate state awareness. A robust estimation method of power system branch impedance parameters is proposed based on improved GM estimation. The method first uses projection statistics and coupling relationship detection to obtain the branch impedance parameters related to the leverage point that has the greatest correlation with the system state estimation results,and treats them as suspicious parameters. Then,based on the generalized maximum（GM）estimation method,the suspicious branch impedance parameters are added to state estimation（SE）as augmented state variables to establish a robust parameter estimation model,and the model is solved based on the primal-dual interior point method. Finally,based on the IEEE-39 node standard system,the simulation analysis of the proposed method is carried out. The simulation results show that the proposed method can effectively estimate the suspicious branch impedance parameters related to leverage points,improve the system’s accurate state awareness ability.