The　W-Cu　alloy　has　been　widely　applied　in　metallurgy,　electronics,　military　and　other　fields　because　of　its　good　arc-resistance,　anti-welding,　heat　and　electricity　conducting　etc.　In　the　recent　years,　attention　to　the　immiscible　W-Cu　alloy　has　been　shifted　to　the　problem　of　stabilizing　the　W/Cu　interface　by　alloying.　However,　there　are　still　research　lacks　of　the　mechanisms　of　diffusion,　segregation　of　alloying　elements　in　this　alloy.　It,　obviously,　will　limit　the　further　optimizing　design　for　the　W-Cu　alloy.　This　work　is　focused　on　the　first-principle　study　of　the　electronic　structure　of　W/Cu　interfaces.　Calculations　showed　that　the　same　alloying　elements　in　W-Cu　system　may　have　significant　differences　in　grain　boundary　segregation　and　interface　segregation　behavior,　and　related　micromechanism　was　revealed.　It　was　demonstrated　that　the　relationship　of　the　segregation　energies　of　Sc,　Ti,　Y　and　In　into　W/Cu　interfaces　and　grain　boundaries　of　pure　W　and　Cu　were　related　to　their　stability.　The　correlation　between　segregation　energy　and　interface　stability　was　also　disclosed　by　the　first-principle　interface　calculation　for　W-Sc　and　W-Y　systems.　Further,　combined　with　the　solute　segregation　calculations　for　the　W/Cu　interfaces,　W　grain　boundaries,　Cu　grain　boundaries　and　the　formation　energy　for　the　Cu　solid　solution,　the　criterion　for　solute　optimizing　selection　for　the　W-Cu　system　was　proposed.　According　to　which,　Y　was　selected　as　the　candidate　alloying　element　to　stabilize　the　W/Cu　interface.　This　work　proposed　a　more　universal　method　for　the　optimal　alloying　element　selection　and　may　provide　a　new　design　method　for　the　development　of　high-performance　W-Cu　alloy.