Abstract: The effects of different Pr_t models on the numerical simulations of turbulent heat transfer of supercritical carbon dioxide in horizontal tubes were systematically investigated using the SST k-ω turbulence model and the predictive capability of different Pr_t models was analyzed by comparing against experimental data. Results show that under the condition of low-level buoyancy, the constant turbulent Prandtl number of 0.85 exhibits a good predictive ability, and the maximum deviation for wall temperatures is less than 5 K. Under the condition of strong buoyancy, larger deviations appear for the predictions using Pr_t=0.85 and the existing models of variable turbulent Prandtl numbers that are corrected for supercritical heat transfer have been demonstrated to be invalid as well. Through in-depth analysis, the turbulent Prandtl number models have profound impacts on fluid flow ＆ heat transfer of supercritical carbon dioxide in the boundary layer, and then determine the turbulent heat transfer performance.