In order to deeply investigate the vapor-liquid two-phase boiling heat transfer and flow characteristics inthe secondary circuit of steam generator,the wall heat flux partition in the subcooled boiling region was divided byusing the RPI model for revising the two-fluid model of the CFD ( Computational Fluid Dynamics) program,andsome published experimental results were used to validate the reliability of the revised mode.Moreover,a casestudy on the steam generator of Daya Bay PWR ( Pressurized Water Reactor) nuclear power plant was carried out,in which the subcooled boiling in the preheating part of the secondary circuit was computed with the revised model,and the distributions of fluid void fraction,speed,temperature and heat flux partition in the preheating part were allobtained.