Abstract: In the present paper, the flow and heat transfer characteristics of subcooled boiling of deionized water was investigated in a vertical rectangular narrow channel at atmospheric pressure. Flow visualization experiments were conducted to study the bubble nucleation on the heating wall. Based on the experimental observations, empirical models were proposed to correlate the active nucleation site density, bubble departure diameter and bubble departure frequency with given flow conditions for 2mm vertical narrow channel. Then, computational fluid dynamics（CFD） models were developed to simulate the subcooled flow boiling in the narrow channel by combining the two-fluid model, the Rensselaer Polytechnic Institute（RPI） wall heat flux partitioning model and the proposed bubble nucleation correlations. The numerical results show excellent agreement with the experimental data under the typical test conditions simulated.