Reducing the grain size of metal materials to nanometer scale is an important method to improve their strength. However, nanocrystalline materials in most cases corresponds to a non-equilibrium state and have a relatively strong tendency to reduce the total grain boundary (GB) area to diminish the energy of the system, which results in significant grain coarsening even at low temperatures. This work is based on the thermodynamic model of the ternary nanocrystalline system, selected TiNbFe alloys as an interesting ternary system and explored its thermodynamic stability. The conspicuous GB segregation tendency of Fe atoms in annealed films is the decisive factor that achieves sufficient thermodynamic stability of nanocrystalline. Ti83.20Nb15.03Fe1.76, Ti79.71Nb15.43Fe4.86, Ti77.28Nb15.88Fe6.85 and Ti75.09Nb15.25Fe9.66 nanocrystalline samples showed excellent thermodynamic stability, which against grain growth up to 400 °C. The calculation of thermodynamic model indicates that Nb solute isn't a GBs segregator in the TiNb binary system, while the Nb element greatly promotes the GBs segregation of Fe atoms in the TiNbFe ternary system. These results enrich the experimental support for solute GB segregation in ternary systems and provide a new strategy for the design of Ti-based nanocrystalline metals with excellent thermal stability.