Offshore liquefaction of natural gas，including associated gas，a ‘by-product’ of offshore oil production and marginal gas field presents several unique characteristics and design challenges including the effect of dynamic sea motion on equipment performance，space and weight limitations，LNG sloshing in inner storage tank and offloading system，and increased safety concerns due to a more compact layout and limited space.Considering the environment condition of South China Sea as well as the specific components of associated natural gas，the overall layout of typical LNG-FPSO unit is first reviewed，and then the various pre-treatment and liquefaction technologies and processes are compared and discussed.In what following，the LNG storage，offloading，power supply and skid-mounted modules are suggested.