Abstract: This paper proposes and discusses a new wall boiling model developed based on our previous experimental work for the 2mm narrow rectangular channel. The new model includes the active nucleation site density, bubble departure diameter, bubble departure frequency and the onset of nucleate boiling（ONB） sub-models. The thermal-hydraulics of the narrow channel was separately simulated by the new model and CFX model under specific experimental conditions. The simulation results of wall temperature and average temperature were compared with experiment data in good agreement. The difference of three main correlations of two models and the ONB sub-model influence on the result were discussed. The results show that the NEW model with ONB sub-model provides better predictions of the thermal-hydraulics in the narrow channel.