The invention discloses a measuring method for seasonally frozen soil thicknesses. The measuring method is based on a principle that ''resistivity of upper layer soil is much greater than that of lower layer soil in a seasonally frozen soil region, the increase of depth of a current electrode in two electrodes buried underground can lead to the decrease of potential difference between two points on the ground surface, and the grounding resistance declines sharply after the current electrode penetrates the upper layer frozen soil, thus a ground surface potential difference change rate decreases drastically'', solves the problem of seasonally frozen soil thickness measurement, is high in measurement precision, provides a reference for the grounding grid burial depth design, and can be further used for evaluating whether an existing grounding grid can meet safety requirements in a soil freezing season.