In the 0.1~10 Hz frequency range of the frequency-domain IP method,the frequency characteristics of the apparent resistivity amplitude determined only by IP effect can be approximately expressed by a linear function of frequency logarithm,and the variation of apparent resistivity amplitude affected by electromagnetic coupling can also be roughly expressed by a power function of frequency.Therefore,multiple frequency measurement is used to remove electromagnetic coupling effect in the frequency-domain IP method.The SQ-3 dual-frequency IP instrument has four frequency groups,and the frequency used is from 1/13Hz to 8Hz,just in the application area of the two approximate formulas.The authors applied the idea of multiple frequency decoupling to process dual-frequency IP data,and put forward the multiple frequency group decoupling method according to dual-frequency IP characteristics.The application of the method to field data processing shows that the decoupling result is satisfactory.