Abstract: The borehole radar is a kind of geophysical exploration tool based on high-frequency pulse electromagnetic (EM) wave transmission for detecting subsurface information. In this work, the transmission characteristics of transient EM wave were studied for designing borehole radar system and interpreting subsurface information. Propagation speed and attenuation coefficient were theoretically studied to find out the distance between the target and the borehole, as well as the maximum detection range of the borehole radar. Based on the theoretical study, we designed a borehole radar system. In order to verify the system, field experiments were carried out in a limestone stratum. The experimental results demonstrate that the system can effectively detect a metal target 8 m away from the borehole.