Abstract: At present, the prediction of the critical heat flux (CHF) in the rod bundles is mostly based on the experimental correlations, which is limited by the specific application range, and cannot be effectively extrapolated or the prediction accuracy is reduced. In order to meet the prediction requirements of CHF in different light water reactors, it is necessary to develop a wide range of CHF prediction methods for different geometries and thermal boundaries. Based on the sub-channel analysis method, the two types of critical phenomena were considered in the paper, which were departure from nucleate boiling (DNB) and dryout, and the CHF in the bundles through coupling subchannel analysis code and the CHF mechanistic model was calculated. By comparing with the experimental data of CHF, it is proved that the coupling code has better prediction accuracy for the CHF in the rod bundles.