Abstract: In the present paper, an advanced sub-channel analysis program, ATHAS, was used to analyze double-row fuel rods assembly of a Supercritical Water Cooled Reactor（CGN-SCWR）, to inspect whether the thermal parameters such as fuel rod cladding temperature meet the safety requirements. Some representative groups of sub-channel parameters depending on both hydraulic diameter and outlet temperature were employed to more detailed study the impact of components on different types of sub-channel. Furthermore, in order to better study the effect of empirical correlations on the heat transfer of cladding, turbulent mixing coefficient, axial friction coefficient and heat transfer correlations were also chosen to make the sensitivity analysis. Results show that all the designed parameters satisfy the safety requirements, and the maximum cladding temperature reached to 685.3℃. The conclusions also suggest that the heat transfer effect was mostly effected by the chosen empirical correlations, for example the maximum cladding temperature difference for different correlations could reach to 41.3℃.