Abstract: The MCNP5 and TSUNAMI-3D-K5 of code system SCALE5.1 were used in this paper to perform calculations and analysis on the fuel nuclides sensitivity coefficient for the molten salt reactor experiment. It is indicated from the results that the fuel nuclides sensitivity coefficient is related to the nuclide fraction, position and neutron reaction cross section. The sensitivity coefficients of macroscopic fission and capture cross section of ²³⁵U with the maximum sensitivity coefficient are 0.267 and 0.110 respectively. MCNP5 and TSUNAMI-3D-K5 results for ²³²Th macroscopic total and capture cross section sensitivity coefficient variation of neutron energy are same, both have a peak around 0.1 eV, and the vibration ranges are consistent with the cross section resonance zones.