Abstract: Using inner floating roof tank to store light oil can decrease the evaporation loss and prevent the environment from polluting. Generally, the semifinished stabilized gasoline coming from the FCC has more gas content with high temperature when it enters into the tank. Therefore, how to select the structure of the inner floating roof is more important. The application of several structures shows that the ring-plate type inner floating roof presents the liquid overflowing problems, which causes the plate to sink; the aluminum-alloy inner floating roof exists corrosion problem caused by impurities in the light oil, which can not avoid the liquid overflowing as well. The annular-cabin type inner floating roof can effectively prevent the gas from building-up at the soft seals of floating roof, and decrease or prevent the liquid overflowing. The liquid can not accumulate on the top of floating roof. It is considered that if the protective coating applies to the floating roof, the structure will be an ideal selection for the stabilized gasoline tank.