Abstract: Standard modular structures of covered floating roof tank are generally workshop manufactured before being transported to the installation site, and then they are launched in the oil tank through man-hole in order and assembled with bolts or rivets.Modular structure of covered floating roof tank is characterized by low cost, short setting time, safe and reliable with higher energy saving rate.In recent 20 years, more than 5.000 modular floating decks have been used in covered floating roof oil tanks, the most of which are made of aluminum floating decks, and their structures are formed in aluminum alloy frames and buoyancy components as pontoon.In this paper, the structure rationality of current modular floating deck in China is analyzed.It is concluded that smaller circumferential stiffness and larger axial stiffness can ensure the modular floating deck to successfully pass through the sticking and prevent being logged and broken.Pontoon is kind of floating component of deck, and the more uniform arrangement of it is necessary.And at the same time, circumferential buoyancy of the modular floating deck should get a little bit bigger.The space between the floating deck and oil surface can ensure safe operation of the covered floating roof oil tank.Because sealing device is a key component of floating deck, the tongue-shaped seal is better.Some design and installation problems in auxiliary components, such as diffuser pipe, cover board, outrigger, venting window and overflow pipe, are also discussed.Although the modular floating deck belongs to an narrow field in the industry, it has been widely applied with remarkable economic and social benefits.Considering lower capacity in development and production for industrial manufacturers, some suggestions in the future development of modular floating deck are proposed.