Offshore platform,which is also called module,like a kind of huge traditional offshore steel structure,comprises various disciplines such as structure,pipeline,mechanical equipment,etc.,and it is usually composed of multi-layer deck. Structural discipline is the fundamental discipline which is at the front end of the whole platform construction process. It includes the column,plate girder,H-shape and some other kinds of structural parts. The size of structural discipline basically decides the whole platform size.The construction of offshore platform usually includes pre-fabrication and final assembly. In design stage,each layer of deck is divided into several panels to be prefabricated,and then,these panels are assembled into a layer of deck by transportation and hoisting and other production links. Thus,there are a lot of factors existing in the construction can affect the size of the platform. The size control of platform construction is discussed in detail.