sigma　and　mu　phases　are　two　of　the　most　common　topological　close-packed　(TCP)　phases　in　nickel-based　single　crystal　superalloys,　which　are　detrimental　to　the　comprehensive　properties　of　superalloys.　It　is　universally　acknowl-edged　that　Ru　plays　an　important　role　in　the　precipitation　of　TCP,　and　its　inhibiting　effects　on　the　nucleation　and　precipitation　of　mu　phases　have　already　been　confirmed,　but　its　effects　on　sigma　phases　remain　vague.　In　this　work,　the　types　and　area　fractions　of　the　TCP　phases　precipitated　from　4　alloys　with　different　compositions　have　been　characterized.　It　is　found　that　Ru　has　different　effects　on　the　precipitation　of　different　types　of　TCP.　With　the　help　of　density　functional　theory　(DFT),　the　interface　structures　between　sigma　and　matrix　gamma　are　further　studied,　and　on　this　basis,　the　effects　of　different　solutes　such　as　Ru　on　interface　stability　and　electronic　structure　are　discussed　in　detail.　Ru,　Re,　W,　Cr　and　Ta　are　able　to　enhance　the　interface　stability,　boosting　the　nucleation　of　sigma　phase.　Co　is　different,　for　it　can　reduce　the　interface　stability　and　elevate　the　nucleation　difficulty　of　sigma.　Additionally,　the　distribution　behaviors　of　solutes　between　sigma　and　gamma　phases　have　been　calculated,　from　which　it　can　be　found　that　the　energies　of　solutes　like　Cr　and　Ru　distributing　in　sigma　are　more　stable　than　distributing　inside　gamma,　and　these　solutes　have　the　tendency　to　diffuse　from　gamma　to　sigma.　These　results　reveal　the　effects　of　solutes　like　Ru　on　the　precipitation　of　sigma　phase　in　terms　of　interfacial　stability　and　atomic　diffusion,　which　provide　a　new　understanding　of　Ru　effects.