In view of the urgent need of heat transfer model and oxidation relationships in pressurized water reactor nuclear subchannel software to improve the core safety and the accuracy of simulation and prediction of domestic software,we used numerical simulation technology to analyze the heat transfer model and oxidation relationships in COSINE subchannel software,and used experimental data to study the influence of different theoretical relationships on boiling heat transfer performance and oxidation amount.The results indicate that the software has the ability to simulate the heat transfer before and after the criticality in the rod bundle,and the simulation results are in good agreement with the experimental values.Before the superheat degree is less than 4 K,the MAX model is suitable for calculating nucleate boiling.When the superheat degree is greater than 4 K,the PLUS model has good applicability.Dougall-Rohsenow model is suitable for calculating film boiling.Baker-Juster model slightly overestimated the oxidation amount before the temperature was lower than 1374 K;When the temperature is higher than 1374 K,the oxidation amount is underestimated.