The problem of karst is often encountered in constructions of hydropower projects in China.Based on the geologic survey data and analysis of the geologic environment, rock, and geologic structure, this paper discusses the distribution pattern and the genetic mechanism of karst. The result indicates that the karst above the left dam abutment is the result of internal and external force coupling effect, and also one of the typical modes of karst formation in northern China. Considering the importance of the spatial location of the karst, this paper discusses the seepage coefficient and studies the seepage problem and the anti-seepage measures according to the field pump-in test. The research result provides a reasonable basis for the selection of the karst anti-seepage scheme.