Abstract: The geological conditions of the extra-long West Qinling tunnel on Lanzhou-Chongqing railway are complex which is characterized by karst, active faults and high geostress. The characteristics of surrounding rocks,structure, geostress, groundwater, karst and so on are evaluated and predicted by comprehensive geological survey-The effect of geological survey is evaluated and the reasons for the difference between survey results and actual conditions disclosed by construction are analyzed based on a comparison with the geological conditions obtained by tunnel construction. The suggestions are proposed such as focusing on the analysis and research of the background of regional geologic structure, implementing drilling verification and carrying out hydrogeological pumping test for the long deep-buried tunnels.