The invention discloses a power system WLAV robust estimation method based on variable substitution. By means of the method, non-linear measurement equation substep linearization of state estimation is achieved by introducing a middle variable. An interior point method is introduced into a measurement equation after substep linearization to conduct WLAV robust estimation, a Hessian matrix is not required to be formed, and meanwhile the number of dimensions of a coefficient matrix in the equation set Karush-Kuhn-Tuckier (KKT) is reduced. Effectiveness of the robust estimation method is verified by a plurality of example simulation results. Compared with a result of the traditional interior point method of WLAV robust estimation, the method has advantages in calculation speed and robust performance and has engineering application prospects.