Leakages usually destroy the stability of an ash dam,so it is important to get the information of the leakage position, the area and elevation of the leakage, and the soakage line of the dam with the purpose of tackling these problems. The measurement of the soakage line and the detection of the leakage distribution as well as the relationship between the distribution and the outflow point therefore constitute the key problem in analyzing the stability of the ash dam and performing the reinforcement of the dam. This paper discusses the geophysical methods for detecting the ash dam leakage and the performance procedure in field survey, and also deals with the effect of these methods. It is shown that such techniques as the spontaneous potential method, the ground penetrating radar, and the high density resistivity method seem to be the effective methods which can be employed to detect the outflow location in front of the ash dam, the inner soakage state of the dam, and the position of the soakage line.