Abstract: To ensure that the predictive capability of the core heat transfer model can meet the safety constraints, the effects of fluoride salt coolant physical parameters on the uncertainty and sensitivity of the core heat transfer models are studied. Statistical uncertainty evaluation method is adopted in this paper. The physical parameters of the coolant including dynamic viscosity, density, heat capacity and thermal conductivity are taken as input parameters, and the classical heat transfer correlation is chosen as the calculation model. The uncertainty of Nu number and its sensitivity to physical parameters are obtained. The results show that the average values of the calculated Nu number are very close and the distribution forms of Nu number are both nearly the normal distributions, regardless of whether the probability distribution of input physical parameters is normal or uniform. At the same time, it is found that the dynamic viscosity is the most important physical parameter that affects the Nu number, and it is negatively correlated. Thermal conductivity is negatively correlated with Nu number. Density and heat capacity have less positive correlations with Nu number.