Karst region is a kind of complicated groundsill.To design tall-buildings built on karst subgrade,precise analyse result is needed.The method based on superstruct-foundation-soil interaction theory can precisely calculate the(internal) force of structural,foundation and groundsill.The method of finite element is an effective way to solve the problem.Finite element analys is software ANSYS is used to analyze superstruct-foundation-soil interaction on Karst Subgrade.Through comparing methods based on superstruct-foundation-soil interaction with traditional analysis method(in this condition,superstruct-foundation-soil interaction is not taken into account),the interactional effect to structure,foundation and rock are discussed.Through the analysis,several conclusion can be drawn as follows: The side stress of column is small for buildings on Karst region,but the side stress of corner columns is much larger than the others.The side stress of shear wall is great and the location of shear wall is significant for the interaction.Slab foundation is effective for Karst region,it plays a great role on interaction.