Abstract: Discloses a kind of built-up inner floating ceiling for use in an oil storage tank, with a view to removing electrostatic effects. The ceiling comprised a skeleton and plastic buoys concentrically arranged thereon, under which there is provided a metallic net in contact with oil, said buoys being pressed from both sides by radial beams of said skeleton, and placed between peripheral beams at rear and front, with a cover plate at top and said metallic net at bottom, so that they are in contact with conductors at any side. Further, wires leading to the top of the oil tank are connected to said cover plates, and said buoys are filled with a conductive additive to remove accumulation of electrostatic charge. Such a floating ceiling can, therefore, be free from any electrostatic effects.