Abstract: The principle of high-density resistivity method was introduced in this paper, and the method was used in the detection of concrete anti-seepage wall of Longtoushi hydropower station dam. By analysis on detection result, conclusion was gotten that the quality of anti-seepage wall was generally good, except the compactness at top was low. This was consistent with the result by water pressure test. As high-density resistivity method is of the advantages that it reflects the distribution of anti-seepage wall concrete, its testing result is obvious and it is convenient for engineering application, it has great prospects for application and popularization．