Abstract: The karst area of China is extensive,almost 30%of the land area.For highways,bridges,dams and other projects,in the site,find out the underground karst or other mining area cave is very important,because they will directly affect the quality and safety of project.In these areas,the geological condition is very complex,to understand the working area of the natural geographical and geological conditions as detailed as possible,can benefit in measuring line of reasonable arrangement and observation system design for the optimization,and initially determine the problems existing in the construction process,to formulate corresponding measures to ensure the high quality of the data acquisition.With a railway as an example,first introduced the theoretical knowledge of electrical prospecting,and related the electrical sounding in the cave exploration in the area of data acquisition,processing and interpretation,to clarify the important application of electrical sounding in the karst exploration.