Abstract: It is prone to encountering water inflow in karst tunnels. To avoid water inflow incidents in the construction of karst tunnel, field geological investigation was adopted to investigate the karst geology conditions in Xinjie tunnel of Kaili ring highway in Guizhou Province. It indicated that karst was extremely developed on the site of Xinjie tunnel, including karst depressions, skinholes and karst caves. Furthermore, there might be a large karst cave in the area where the tunnel passed through, and the probability of karst water inrush was high. In order to prevent karst water inrush incident, geological prediction by ground penetrating radar was applied to detect the geology conditions in front of the tunnel face. The results of geological prediction at two typical tunnel faces were analyzed and compared with the geological conditions exposed by subsequent excavation, which show that the geological prediction by ground penetrating radar had detected the geological conditions in front of tunnel face efficiently and could provide supports for safe excavations.