Abstract: This paper takes the external floating roof steel tank, a storage capacity of 10×10⁴ m³, in Huangdao National Oil Reserve Base as an example, and introduces main structure of large-scale floating roof tank. Structurally, the tank is a kind of external double-deck floating roof tank composed of tank bottom, tank wall, floating roof and wall reinforcement ring, wind girder, winding ladder platform, rotating stairway and several auxiliary facilities, including electrostatic conductor, water drainage system and edge seal of floating roof. The relevant safety accidents can be primarily classified into fire and non-fire accidents, in which fire accident can be further divided into sealing ring fire, floating roof pool/bund pool fire, full-area fire and tank group fire, and non-fire accident subdivided into mechanical faults of tank body, including buoyancy chamber leakage, tank body fracture, insufficient tank body strength due to corrosion, and floating roof sinking, and improper operation accident. The main factors causing an accident are lightning stroke, open flame, quality defects and improper operations.