Abstract: Application of magnetic flux leakage(MFL) testing to the detection of corrosion in atmospheric storage tank floor was studied. Five storage tanks of more than 1000 m3 were inspected by using FLOORMAP 2000 tank floor magnetic flux leakage scanner and the corrosion information of the tanks was showed. It was proved by comparative analysis of the results of MFL inspection, visual examination and ultrasonic thickness testing that MFL inspection was reliable. On the other hand, the main reasons for the corrosion and failure of tank floor were analyzed comprehensively.