Abstract: To analyze the complex transient characteristics in voltage and current observed in global earthing systems (GES) under fast impulses,an iterative learning analyzing methodology (ILAM) is proposed for non-linear parameters (NP).Firstly,the mathematical formulation for analysis of NP in GES under fast impulses is built; then the influence of the pre-and post-ionization resistances on the voltage and current is surveyed and ILAM is established for NP in GES based on the ideology of ILC,where the correction pre-and post-ionization resistances is conducted during the tracking of the field-test voltage and current.In doing so,the non-linear relationship related to the time of pre-and post-ionization resistances is determined.Finally,the established methodology is validated by simulation.Results show that by the method,the maximum relative tracking errors in voltage and current stand at 2.82% and 6.97% respectively after adequate iterations.Thus,it may be utilized to analyze the time-varying NP in GES conditionally.