Three kinds of through-the-earth communication technology, inductive coupling by antenna, current injection by means of ground electrodes and transmitting by elastic wave, were introduced, as well as the operating principles, performance and characteristics of stratified earth channel were also discussed. And the propagation attenuation, frequency band and power efficiency were analyzed and compared. Conclusions can be drawn as follow: the communication system by ground electrode is more prospecting among the three, though the loop antenna scheme is popular recently;the efficiency of ground electrodes scheme is higher than that of the rest two methods;the communication of elastic wave method is more influnceable by the Mechanics characteristics of the earth layer, especially when it is soil.