The floating production, storage and offloading system for liquefied natural gas (LNG-FPSO), is a new conceptual unit and an effective and realistic way for exploitation, recovery, storage, transportation and end-use applications of marginal gas fields and offshore associated-gas resources. However, a real LNG-FPSO unit cannot be built unless some breakthroughs in many key technologies are produced. Many unique characteristics of LNG-FPSO, such as restricted space, platform motion, LNG sloshing in inner storage tank and offloading system, which have not been considered in the onshore projects, are the most rigorous factors to be taken into account during design. In this paper, the overall layout of a typical LNG-FPSO unit is reviewed; the leading liquefaction technologies and processes are compared and discussed. Taking the effects of the vessel motion and limited space into account, the applicability of the main systems and key equipments of storage, offloading and power supply, are analyzed.