A　model　for　describing　solute　segregation　at　grain　boundaries　has　been　developed　for　substitutional　solid　solution　alloys,　which　integrates　multiple　factors　from　atomic　to　microstructural　scales.　A　concept　of　mo-lar　Gibbs　free　energy　of　segregation　was　introduced　to　evaluate　the　segregating　capability　of　the　solute　elements　in　a　closed　system,　through　which　the　influences　of　grain　boundary　structure,　grain　size,　ma-terial　composition,　and　external　conditions　were　described.　Based　on　the　evaluation　of　various　energy　forms　related　to　solute　segregation　and　grain　growth　processes,　the　nature　of　the　thermal　stabilization　of　nanograin　structures　by　solute　segregation　was　disclosed.　A　criterion　for　the　destabilization　of　nanostruc-tures,　which　is　determined　by　the　competition　of　the　change　rates　between　the　molar　Gibbs　free　energy　of　segregation　and　the　total　energy　of　grain　boundaries　with　grain　size,　has　been　proposed.　This　study　provided　guideline　to　achieve　high-temperature　stability　of　nanograin　structures　of　solid　solution　alloys　even　for　the　weakly　segregating　nanocrystalline　systems.&　COPY;　2023　Published　by　Elsevier　Ltd　on　behalf　of　The　editorial　office　of　Journal　of　Materials　Science　&　Technology.