当利用自然电位法（ＳＰ法）在火山岩地区勘探地下水时，发现负的自电异常大小与地下非饱和区厚度之间存在一个线性关系．从理论上对该经验关系进行探讨，并提出针对这一水文地质问题的自电测量解释方法．最后给出法国中央高原ＬａＣｈａｉｎｅｄｅｓＰｕｙｓ地区的勘探结果 When using the natural potential method (SP method) to explore groundwater in volcanic areas, we found that there is a linear relationship between the magnitude of negative self-anomalies and the thickness of unsaturated zones in the underground. This empirical relationship is discussed theoretically and the self-electric interpretation method for this hydrogeological problem is proposed. Finally, the exploration results of the LaChaine des Puys region of the French Central Highlands are given