The invention discloses a method for obtaining ionization discharging initial field intensity of soil around a grounding conductor under impulsion. An earth rod and a cylindrical backflow electrode structure are adopted to test, and a changing curve of the resistance of the soil between the earth rod and the backflow electrode is measured, wherein the resistance of the soil changes along with applied impulse voltages; a slope of the changing curve is adopted to deduce a real voltage of ionization discharging, and through an electromagnetic field theory, the corresponding ionization discharging initial field intensity of the soil around the ground connector is obtained. Because the ionization discharging initial field intensity of the soil around the grounding conductor under the impulsion is obtained through the resistance variation of the soil between the earth rod and the cylindrical backflow electrode, results are more objective; because the earth rod and the cylindrical backflow electrode structure are adopted to test, the earth-rod surface field intensity is more uniform. The method can be applied in measuring discharging features of the soil around the ground connector and instructing grounding engineering construction.