This paper introduces the mechanism of applying Ground Penetrating Radar(GPR) in the advanced detection of subsurface conditions in the tunnel construction.In this case history,the GPR Model RIS-K2 was used to determine geotechnical and geological conditions in the Longxing-2 tunnel entrance excavation.Combined with other observations such as,topographical and exposed conditions at the tunnel face,the conditions of the area to be excavated are evaluated and predicted.The advanced detection by a GPR provides a basis for real-time design of a safe excavation in tunnel construction.This paper sheds some light on the experience accumulated in applying GPR in the tunnel construction.