Abstract: Compared with mud pulse transmission, electromagnetic wave transmission while drilling has the advantages of not relying on drilling mud medium circulation and fast information transmission. In addition, electromagnetic wave transmission is sensitive to formation resistivity, which is convenient for timely discovery of mineral target layer. Based on the above characteristics, the electromagnetic wave transmission system while drilling has been more and more widely used in the exploitation of oil, natural gas and coal-bed methane (coal mine) in recent years. In this paper, the transmission of electromagnetic wave while drilling in the formation channel is analyzed by equivalent circuit method according to the propagation law of electromagnetic wave in the formation and the near-field radiation characteristics of extremely low frequency (ELF) electromagnetic wave which is different from the previous methods. In addition, according to the results of equivalent circuit analysis, the magnitude of the instantaneous change rate of the envelope of the electromagnetic wave signal amplitude received on the ground is used as the condition to judge the resistivity characteristics of the formation. The practical results of Qinshui coal seam exploration in Shanxi Province demonstrate that the method proposed in this paper has obvious timeliness in the exploration of coal and other mineral resources, and further proves that the electromagnetic wave information transmission system while drilling can also be used as an effective real-time logging system.