In　a　tungsten-based　alloy　system,　the　appropriate　solute　elements　are　selected　to　produce　strong　segregation　effect　to　reduce　the　interfacial　formation　energy,　which　can　effectively　improve　the　mechanical　property　and　thermal　stability　of　the　system.　Based　on　the　first　principles　calculation,　the　solute　segregation　model　of　tungsten-based　alloys　is　constructed.　The　W-In　alloy　is　taken　for　example　to　study　the　grain　boundary　segregation　behavior　and　bonding　characteristics　of　solute　at　different　concentrations.　The　bonding　of　the　W-In　system　is　revealed　from　the　electronic　structure,　and　the　variation　of　the　interface　stability　of　the　W-In　system　with　the　solute　concentration　is　predicted.　Based　on　the　electronic　structure　analysis　of　bond　population,　differential　charge　density　and　density　of　states,　the　bond　transition　characteristics　of　solute　atoms　in　the　W-In　system　in　the　segregation　process　are　found,　and　the　microscopic　mechanism　of　the　W-In　bond　transitioning　from　the　ionic　bond　inside　the　grain　to　the　strong　covalent　bond　in　the　grain　boundary　region　is　elucidated:　the　difference　between　the　grain　boundary　and　the　intragranular　structure　leads　to　a　decrease　in　the　valence　state　of　the　W　atom　in　the　grain　boundary　and　the　oxidizability　is　weakened,　eventually　leading　to　the　W-In　bond　transition.　The　non-monotonic　variation　of　the　intrinsic　segregation　energy　of　the　solute　with　the　concentration　of　In　in　the　W-In　system　is　obtained.　The　mechanism　of　the　influence　of　solute　concentration　on　the　intrinsic　segregation　energy　is　revealed　by　analyzing　the　bond　interaction　and　energy:　the　solute　concentration　remarkably　affects　the　bond　strength　before　and　after　the　W-In　bond　segregation,　resulting　in　a　significant　decrease　in　the　segregation　ability　when　the　solute　concentration　is　close　to　0.0976,　and　finally　the　variation　of　the　segregation　energy　with　solute　concentration　is　obtained.　Based　on　the　analysis　of　the　phase　mechanical　stability　and　the　solute　segregation　in　the　grain　boundary,　without　considering　the　vacancy　concentration,　the　optimal　solute　concentration　range　and　the　range　that　needs　to　be　circumvented　in　the　W-In　alloy　system　with　high　thermal　stability　are　predicted　by　the　calculations　of　the　model,　which　are　0.106-0.125　and　0.0632-0.106,　respectively.　This　study　provides　theoretical　basis　and　quantitative　guidance　for　designing　and　preparing　the　tungsten-based　alloy　materials　with　high　thermal　stability.