The effectiveness and safety of irreversible electroporation（IRE） in tumor therapy has been proved by clinical applications for many years. The high-frequency irreversible electroporation（H-FIRE） proposed recently has both the advantages of the conventional IRE and the benefit of inhibiting the muscle contraction during the treatment. However

the mechanism of tumor ablation is unknown yet. We tried to analyze the difference between IRE and H-FIRE in tissue ablation based on impedance spectrum. The variation of the impedance spectrum of the New Zealand White Rabbit liver was studied when treated by both conventional IRE and H-FIRE

and then the circuit model was used to fit the impedance curve and extract the information from the change of the impedance spectrum. The results showed that the impedance spectrum of the tissue changed significantly when treated by pulses and the impedance mode variated significantly in the low-middle frequency while the impedance phase changed significantly in the middle-high frequency with the direction from negative values to zero. After fitting the impedance data to the circuit model

the information showed that the change of the extracellular resistance decreased significantly because the new pathway for current was in parallel with the extracellular resistance. The change of the extracellular resistance induced by conventional IRE was larger than that induced by H-FIRE when they had the same pulse dose

and among the H-FIRE

the change would go with the increase of pulse duration. The variations of the impedance and the elements in the circuit model can reflect the degree of IRE accurately and is expected to be an effective approach to detect the outcome of IRE in clinical.