This paper makes a fairly systematic study of electromagnetic coupling (EM)phase frequency spectra of (lipole-dipole array in horizontal two-layered earth. It is considered that the electrical parameter μ₂(relative electric con ductivity) and geometric parameter h₁/a(thickness of cover/dipole distance) are major factors affecting properties of EM in two-layered earth. The two-layered earth whose bottom layer has high resistance shows a rather strong EM effect, and such an EM effect only reflects the shallow layer; if the bot tom layer has low resistance, the EM effect reflects the distribution of com paratively-deep-seated electric bodies. An analysis of parameter regularity of EM frequency spectra and inversion shows that the variation in EM cha racteristics might directly indicate the variation in resistivity of underground media.