Abstract: Semi-empirical correlations are accurate to predict the properties of binary mixture of noble gases, based on the Chapman-Enskog approach for dilute gases after correcting the effect of high gas density, and using the law of corresponding states. A code based on Fortran 95 was developed to predict the physical properties of helium xenon mixture. It was used to analyze the helium-xenon mixture properties change in the relationship between molecular weight, temperature and pressure. The effects of the physical properties change on adiabatic coefficient, convective heat transfer performance and resistance characteristic of space Brayton cycle were also analyzed. The results show that at pressure of 2.0 MPa and temperature of 400 K, the adiabatic coefficient of helium xenon mixture increases with molecular weight from 0.40 (pure helium) to 0.44 (pure xenon), the normalized heat transfer coefficient of helium-xenon mixture to that of pure helium increases firstly and then decreases with molecular weight, and the maximum normalized heat transfer coefficient occurs at a molecular weight of 15 g/mol. The normalized pressure loss coefficient monotonously increases with molecular weight. These analysis results can be applied for the design of space nuclear reactor power.