It is of great necessity and importance to make advance karst prediction during tunnel construction in karst area. Researching on the karst development mechanisms, which falls in the scope of geological analysis methods, plays a basic and guiding role in the advance karst prediction in tunnel construction. The authors introduce the task of advance geological prediction in karst tunnel and the status of study on karst development mechanisms in this paper. Furthermore, taking Changleshan tunnel as an example, they study on the karst development and distribution pattern. On basis of the study results, they make geological forecasts and explain the forecast results, which achieves good prediction results.