Abstract: Inner floating roof tanks for product oil storage see a rapid development for the purpose of ninumizing the product loss due to volatilization. Especially, fabricated inner floating roofs are well received due to the fact that they need no welding and all their parts are accessable through the manhole in the tank. On the basis of investigations on the design. fabrications and applications of the inner floaling roofs in China, this paper mentions the following points which need attention in design: ① Determination of design load: the concentrated, active design load for floating roof shall not be less than 2268 N, and the uniform, active design load for the support leg shall not be less than 610 Pa. ② Determination of buoyancy of the floating roof: the buoyancy of floating roof is a critical parameter in design, because it has a direct influence on the safe operation of the roof; the buoyancy is generally designed as much as two times the roof's weight. ③Determination of roof size: while roofs having a too small diameter will result in oil vapour effusion from the gap between tank wand and roof rim, an over sized roof will lead to strained roof migration.