Abstract: The defects repair methods about corrosion, leakage, and crack of bottom plates of floating roof tank are introduced. Five maintenance practices are given by means of several oil tanks used in Luning Pipeline. The maintenance program is composed of two steps: one is to adopt the multiple methods to inspect the corrosion before repair, and the program will be determined according to the evidence of corrosion obtained; the other is to select the methods of welding, grinding, displacement of partial or overall plate, or the combination in the light of status of different kinds of corrosions. The paper introduces the detail inspections and repairs for the five tanks, as well as the repair measures set forth during the maintenance.