This paper deals with the standing wave resulting from the interference of the reflection electromagnetic wave when the electromagnetic wave is transmitted and perpendicular to the strata. The conditions of antinode and node formed on the ground are also discussed. According to the equation deduced by the author, the thickness of the strata and the relative sizes of the electromagnetic parameters in the media on the two sides of the bottom interface of the strata can be determined by measuring the frequency of the antinode. It is also pointed out that at least four natural electromagnetic wave sources can be used in geophysical exploration based on the electromagnetic standing wave method.