Abstract: Bubble departure diameter model is an important sub-model for wall boiling calculation. In order to predict the wall heat transfer accurately, this paper models the bubble departure diameter in subcooled flow boiling by using the force balance method with a new improved bubble growth model. Bubble growth model considers the contribution of microlayer, superheated layer and subcooled liquid layer at the top of bubble to bubble growth. It is validated through the comparison with the saturated boiling and subcooled boiling experiments, and the prediction results show good agreement with the experimental data. Three databases for subcooled flow boiling are selected to validate the bubble departure diameter model, and the predictive accuracy is in acceptable error range.