The concept of "tunnel karst disease risk estimation" is put forward for the first time, which is applied in advance geological forecast of Shajinjie tunnel. This method can help us recognizing the main hole advanced prediction work to improve the forecast work pertinence. In the forecast method, it takes the head in integrating the surface high-density electrical method with the georadar method, which improves the forecast accuracy of serious karst disease. The actual excavation results show that the advance geological forecast results meet the actual situation highly.