Structural　stability,　magnetic　properties　and　electronic　structures　of　SmCo4.5M0.5　alloys　with　doping　elements　of　transition　metals　M　=　Ti,　Zr,　Hf,　Mn　and　Cr　were　studied　systematically　based　on　the　first-principles　calculations　and　statistical　thermodynamics.　It　was　found　that　the　addition　of　Ti,　Zr,　Hf　and　Mn　was　beneficial　to　the　stability　of　the　SmCo5　phase,　while　doping　of　Cr　was　detrimental.　The　effect　of　temperature　on　the　site　occupancy　of　the　doping　elements　was　studied,　which　showed　that　the　SmCo4.5M0.5　ternary　alloys　can　be　stabilized　by　doping　Mn,　Ti　and　Hf　in　a　wide　temperature　range.　The　calculations　for　magnetic　properties　indicated　that　the　total　magnetic　moment　of　the　SmCo5　system　was　usually　weakened　by　doping　non-magnetic　elements　to　some　extent,　however,　doping　Mn　can　increase　the　total　magnetic　moment.　The　magnetic　properties　of　the　doped　SmCo5　system　were　analyzed　based　on　the　electronic　structure.　It　revealed　that　Mn　exhibits　obvious　magnetism　in　SmCo5　and　has　little　influence　on　the　magnetic　moment　of　the　surrounding　Co　atoms,　leading　to　an　improved　overall　magnetic　moment.　Based　on　the　combination　of　phase　stability　and　magnetic　properties,　Mn　is　proposed　as　the　optimum　doping　element　among　the　investigated　transition　metals　for　the　SmCo5　system.　(C)　2019　Elsevier　B.V.　All　rights　reserved.