Abstract: On purpose of accurately simulating the subcooled boiling and then predicting the critical heat flux (CHF), subcooled boiling coupled with conjugate heat transfer was modeled based on two-phase CFD approach and interfacial transfer. This numerical approach was proved by typical fuel pin simulations firstly. On the basis of boiling two-phase flow in a fuel subchannel, a CHF prediction method, whose process is similar to CHF experiment, was developed using the wall temperature rise as a criterion. Through this method, the CHF in a fuel subchannel was simulated. The results show that the CHF prediction method developed in this paper can be used for CHF prediction in fuel assembly or other heat transfer systems and provides a new tool for the design and optimization of fuel assembly.