Abstract: Small gas-cooled nuclear reactor systems almost regard the helium-xenon mixture (He-Xe) as the cycling working fluid and reactor core coolant. With the recommended mixing ratio, the Prandtl number (Pr) of He-Xe is as low as 0.2. The RANS method is the main method on the CFD computation of nuclear engineering, which needs the turbulence model and Pr_t model. Previous studies have focused on the effect of Pr_t model on He-Xe heat transfer, but the role of turbulence model in heat transfer calculation has not been deeply discussed, which brings misunderstandings to the subsequent model development or RANS calculation. Therefore, in this paper, the RANS method is used to study the flow and heat transfer of He-Xe in a parallel channel, and the applicability of turbulence model and Pr_t model is studied in order to clarify the influence on the heat transfer simulation. The results show that the k-ω type models are the preferred turbulence model for the channel flow, and existing Pr_t models still need to be improved to satisfy the heat transfer simulation of He-Xe. The selection of turbulence models is equally important for heat exchange calculations. It is suggested that the combination of the two kinds of models should be considered in the development of Pr_t models for He-Xe or RANS analysis.