Abstract: In the detection of dam foundation, singlehole acoustic method, crosshole acoustic method, and seismic velocity method are usually used. In the practical work, the seismic velocity method is mainly used to evaluate the integrity of the whole lithology of foundation and the distribution of the karst fissure. Acoustic method can determine the depth distribution of geological defects like karst fissure. Combination of single-hole and cross-hole acoustic method can make it better to determine the distribution of geological defects of the whole rock. The accuracy of dam foundation detection can be improved if these two methods are used jointly. Comprehensive geophysical methods are applied in the Yinpanjiang River hydropower station and good results are achieved. They provide effective and scientific guidance to the construction units.