Abstract: Karst is a process and result of groundwater geologic function and is one of bad geological phenomenon facing tunnel construction.It is important for construction of tunnel to study the distribution and growing rules of karst area. The lithology and the hydrological conditions had been investigated by means of drilling and physical exploration.Based on the analysis of the geological structure,cover property,namely distribution,sizes and filling of karst,the extent and rule of karst development were clarified.It sums up the karst ecological environment of XangJang tunnel,analyses the construction adventure of karst to track,and put forward the corresponding keeping away steps,and this supplies reference to the specific project of this section.