Abstract: By using Fluent code, the numerical simulation of pressure and temperature profiles was carried out for the hot gas mixing structure of HTRPM and its scale model experiment installation. The mixing performance and the resistance property of these two structures were analyzed. The characters of mixing performance and the coefficient of flow resistance were obtained with the change of Re for flow in hot gas tube. The self-simulation mode of the flow and heat mixing of the mixing structure entrance was discussed. According to numerical simulation and theoretical analysis, the heat mixing performance and the flow resistance property can be obtained by the scale model experiment. However, the flow resistance property should be described in a more detailed and reasonable way which requires the accomplishment of the experiment.