Abstract: Taking into account of the existing shortcomings in real-time monitoring method for the leakage in bottom plate of oil tank by means of the current ways used extensively such as those based on oil level change in tank and sensory inventory check, a new method to real-time monitor the leakage in tank bottom has been proposed. It realizes the leakage monitoring by use of detecting oil vapor volumetric fraction in the pores drilled in the tank foundation, gives the leakage detection principle: on the tank foundation every 9 m (arc length) drill a leakage detecting pore which arrives to the sand cushion, make use of the high-sensitivity oil vapor detector to detect the oil vapor volumetric fraction in the pores, can judge if the tank bottom leaks or not, reviews the operational procedure and scene application, identifies the effectiveness of the method by a case, and describes the technical requirements in detail. Based on the summary and analysis of scene experimental data, the criteria for judging gasoline tank bottom leakage has been proposed, provides useful reference for the oil depot expansion and retrofitting in future.