Electromagnetic method as the important branch of geophysical exploration

has now been widely used in imaging underground structure

and often joints work with other geophysical and geological means

used to identify hidden underground geological conditions. Electromagnetic detection depth has been the geophysical and geological workers’ very concerned problem

the electromagnetic method development

probing depth definition

as well as the common electromagnetic method （frequency domain

time domain） of probing depth and influence factors are introduced in this paper

and it is briefly summarized and analyzed.