Abstract: The leakage of the oil-tank floor is a commonly existing problem in vertical cylindrical steel atmospheric pressure oil-tank. Leakage testing of oil-tank floor is a time-lasting and very difficult technical job. This article intends to introduce the leakage testing theory, procedure and result of oil-tank floor by AE testing. AE testing can locate the leakage points exactly and high efficiently and greatly reduce the actual inspection work-load, testing blindness and testing time. So, the AE testing is a very important and meaningful method, and worthy of being used widely in the oil-tank floor inspection.