Abstract: Karst is the main geological problem in southern Hubei section of Beijing-Zhuhai Speedway. This paper has put forward a comprehensive geological method of engineering mapping, engineering geophysics and drilling based on the analysis and the study of the geological background, development factors and degrees. With this method, the spatial distribution characteristics of the karst, and its development regularity and relations to the formation of caves have been so clearly explored that this has provided correct and precise parameters for the design.