In order to accurately detect the location and range of dam leakage channels and reduce the influence of the limitation and uncertainty of single method on the detection result, a method of combining high-density electrical method and comprehensive tracer method to detect the hidden dangers of dam leakage is proposed. The verification of a pumped storage power station example shows that, the results of the high-density electrical method can be verified by the comprehensive tracer method through several tracing tests. The dam leakage channel detection technology combined with high-density electrical method and comprehensive tracer method accurately reveals the location and range of the hidden danger of dam leakage, overcomes the non-unique defect of single method detection result. The combination of high-density electrical method and comprehensive tracer method for dam leakage channel detection has high efficiency and accuracy.