Abstract ； Research purposes ： Nanjing - Anqing High Speed Railway is located in hily region of the south of the Yangtze River， with many lakes and ponds， complex geological conditions， and widely distributed karst alongthe railway. The areas of carbonate distribution have karst development， and corrosion phenomenon is obrious， karst development degree is medium development and intensive development，the cave is bead - shape，high - speed railway construction is facing how to effectively identify the physical geographical and geological conditions， according to the karst development degree， choose the suitable scheme for subgrade and bridge， and to control the settlement of the structure. Therefore，the investigation and exploration methods of karst areas and the corresponding structural design schemes are carried out to ensure the reliability of tlie design. Research conclusions;( 1 ) The karst prosj^ecting should be fine investigation and analysis， advance planning organization，implementation of scientific management，which should adopt the core drilling test，seismic CT method and wave tube technology of geophysical exploration，to find out karst development and distribution of tlie karst area. (2) In the karst development area，considering the difficulty and cost of the project，it is suggested that the railway should be replaced by the bridge. (3 ) The subgrade in karst areas should be designed according to the princij^le of 11 first exploration，post irrigation and exploration irrigation" . (4) The bridge pile foundation in karst area should be arranged according to the pile drilling data, the distribution of the pile foundation is arranged，the pile foundation needs to penetrate the cave, and is supported on the bottom stable bedrock. (5) The research results can provide theoretical guidance and scientific basis for geological exploration，exploration and structural foundation design in karst area.