Abstract: The method of leak detection by using the oil vapor volumetric fraction in the pores drilled in the tank foundation is not very efficient for cave on-wall oil tanks. In this regard, the leak detection method by monitoring the oil and gas volumetric fraction in the buried pipes in the tank foundation is proposed, which contains more detection point, and the necessity of finding a new method to detect leak in tank bottom is discussed. The principle and operation specification of the new method are introduced, and the cautions in application are explained. Through comparison of these two leak detection methods, the technical features and applicable scope of the new method are summarized, providing beneficial reference for the construction and transformation of the oil storages.