Abstract: Based on the user-defined function (UDF) of the computational fluid dynamics (CFD) code FLUENT, coupled with the neutron dynamics model, fuel rod heat conduction model and uncertainty analysis code SIMLAB, the uncertainty analysis platform CFD/PFS was developed. Thereafter, CFD/PFS platform was used to simulate the unprotected overpower transient (UTOP ) accident of the SNCLFR-10 reactor, and the uncertainty quantification evaluation was performed. Furthermore，the results of uncertainty and sensitivity analysis were discussed. Research result shows that the neutronics and thermal-hydraulic coupling calculation of CFD/PFS platform has good reliability and accuracy. The nominal values of transient parameters are within the bilateral tolerance limits, and the relative deviation between the nominal values and the limits is less than 3.95%. The Doppler coefficient is the main source of uncertainty and has the most significant effect on reactor safety.