Abstract: Two fluid model integrating a set of closure relationships (such as inter-phase heat transfer model, interphase mass transfer model, inter-phase momentum transfer model, mean bubble diameter model, bubble departure diameter model, bubble departure frequency model, onset of nucleate boiling model, wall heat flux partition model) was applied to solve the local flow and heat transfer of subcooled flow boiling under low pressure. The inter-phase mass and momentum energy transfer due to the phase change were added to the mass, momentum and energy conservation equation for liquid phase and vapor phase respectively using the user defined function in CFX4.4. And the subcooled flow boiling was researched in annular channel with inner tube heated uniformly and adiabatic outer tube under low pressure and local flow parameters such as volume fraction, liquid velocity, vapor phase etc. were obtained. The subcooled flow boiling results predicted in this paper were compared to the subcooled flow boiling experimental results of Lee etc., and they agree well.