Due to the complexity of the near-region field and the limitation of the frequency domain electromagnetic sounding used at present, the near-region frequency domain electromagnetic sounding remains an unsolved problem in geophysics. Based on the theory of near-region field, the present paper, by introducing the theory of combination wave, has put forward a definition formula of apparent resistivity suitable for near-region frequency domain electromagnetic Bounding. Such an apparent resistivity can effectively suppress background field in the near region, make prominent the function of geoelectric anomaly information, and reflect objectively electric variation regularity of geoelectic section.