Abstract: It has high risks for the construction of breakthrough section of a large-section karst tunnel, and water burst, mud burst and collapse are often encountered. Accurate geological survey is one of the key measures to realize safe and efficient breakthrough of a tunnel, however it is difficult to meet the accuracy requirement of exploration by traditional geophysical prospecting of reflective seismic wave or electromagnetic wave. A penetration prospecting of geological condition of breakthrough section of a large-section karst tunnel was conducted by radio wave penetration method considering the high reliability of penetration geophysical prospecting and spatial characteristics of the breakthrough section of the tunnel, a small dot pitch based radio wave penetration prospecting for the large-section tunnel was proposed and successfully applied in the construction of Huayingshan tunnel, and good results were obtained and no water burst occured.