Abstract: In nanostructured alloys, grain boundary volume fraction significantly increases with the decreasing of grain size, which leads to high driving force for grain growth. So nanocrystalline metals and alloys are unstable when heating or even at room temperature, which limits its processing and application. Thermodynamic stabilization tendency of Cu-6.5at% Zr and Cu-6.5at% Nb nanocrystalline alloys were calculated and predicted based on the modified Trelewicz/Schuh (TS) model. These two nanocrystalline alloys were prepared by mechanical alloying and annealed at different temperature. Experiment results and theoretical prediction show that, with the addition and segregation at grain boundary of solute atom, grain growth is retarded and thermodynamics stability of these two alloys is enhanced.