For the purpose of more effective underground communication, UHF radio wave propagation along underground gallery was discussed both experimentally and theoretically. From the experimental results, it became clear that the higher frequency bands, i. e. more than 500 MHz, were favorable for underground use by the reason of the lower propagation loss. To establish the propagation model of UHF radio wave theoretically, both the simple geometrical image source method and the characteristic equation method were discussed to allow for gallery conditions such as timbering methods, cross sectional area and others. Reasonably good agreements were observed between experimental results and theoretical calculation which is based on the simple geometrical image source method.
