Abstract: To explore more efficient ion extraction methods used in atomic vapor laser isotope separation (AVLIS), RF resonance method of ion extraction is studied by theory and PIC simulation. The results show that sheath plasma oscillation occurs under weak magnetic field, and its frequency conforms the theoretic result. Resonance occurs when the AC voltage with the same frequency is applied to the electrodes. Amplitude of the oscillation and the current increase, and the voltage of the maximum in the plasma can be as several times high as the amplitude of the applied voltage. Compared with parallel plate static electric field method of ion extraction, RF resonance method increases the ion flux and shortens the extraction time. To achieve the same extraction time, the amplitude of the AC voltage in the resonance frequency can be less than that of the DC voltage with one order of magnitude.