Accurate evaluation of the location of onset of significant void (OSV) is particularly important in predicting the void fraction profile in the subcooled flow boiling. In this study, a Computational Fluid Dynamics (CFD) model based on a wall heat flux partition algorithm is presented. Good consistency between simulation results and available experimental data for void fraction, liquid temperature, and wall temperature is demonstrated for a given case. To further evaluate the feasibility of the CFD model in predicting the OSV condition, more simulations are performed under various operational parameters. The simulation results show that an acceptable prediction is observed in the inlet and outlet sections for the void fraction in all the cases compared with experimental data. In addition, the relative enthalpy of the flow at OSV decreases with a rise in heat flux and with decrease in mass flux and with increase in pressure obviously, which coincide well with the experiments. Meanwhile, the change trends for the liquid subcooling at OSV of the simulation results and the results calculated by Saha and Zuber correlation are similar and the error is within −7.15 to 8.09 K. Therefore, the CFD model can obtain a comparatively accurate liquid subcooling at OSV.