Abstract: The differences of evaluation method of the tank bottom at home and abroad were discussed and contrasted. A petrochemical plant of 10 000 m3 was inspected by using FLOORMAP VS2i tank bottom magnetic flux leakage scanner and the corrosion information of the tanks was shown. It was proved by comparative analysis of the results of MFL inspection, visual examination and ultrasonic thickness testing that MFL inspection was reliable. This paraffin oil tank bottom was integrity evaluated after repairing based on API 653 code and SY/T 5921 regulatory requirements.