In order to study the effective detection depth of the wide field electromagnetic method (WFEM) under the condition of transition zone, the authors designed four geoelectrical models, i.e., homogenous half space, two layers section, three layers section and four layers section, with the skin depth-apparent resistivity curves obtained by forward calculation. Taking magnetotelluric sounding (MT) for reference, the authors made a comparative study of the detection depth of the wide field electromagnetic method and the controlled source audio magnetotelluric method (CSAMT) at the same transmit-receive distance. The results show that the wide field electromagnetic method can be measured in the transition zone and can get larger detection depth with the smaller transmit-receive distance.