Regular boiler feed water treatment system is not suitable for offshore thermal recovery platform because of its characters of long procedure of process, large area occupation and complicated maintenance. Seawater desalination plan fit for offshore platform is studied based on offshore production and environmental features. Boiler feed water treatment systems that can produce steam of different dryness are proposed by comparing the seawater pretreatment schemes, deoxidation schemes and desalination schemes. The schemes proposed in this study has been applied in the design and construction of Bohai Oil Field thermal recovery and offer practical references of boiler feed water treatment system design.