The　segregation　behavior,　the　stability　and　strengthening　energy,　and　the　electronic　structure　of　Ce　at　the　TiAl3/alpha-Al　interface　was　studied　by　first-principles　method　to　understand　the　mechanism　of　the　action　of　Ce　on　the　second　phase　TiAl3　in　Al-Ti-B-Ce　refiner.　The　results　show　that　Ce　can　spontaneously　segregate　at　the　nucleation　interface　of　TiAl3　and　Al　to　improve　the　stability　of　TiAl3/alpha-Al　interface,　and　the　stability　of　Ce　central　site　of　TiAl3(001)　(Al)/Al　(001)　interface(0A0H)　is　the　strongest.　As　for　0A0H　interface,　Ce　has　little　effect　on　the　electronic　structure　of　Al　(001)　side　of　TiAl3/alpha-Al　interface　which　limits　its　direct　refinement　effect　on　alpha-Al,　while　there　is　a　strong　bonding　force　to　Al　atoms　on　the　TiAl3(001)　side　to　reduce　the　surface　energy　of　TiAl3,　change　the　selective　growth　orientation　of　TiAl3,　and　provide　more　nucleation　substrate　to　promote　alpha-Al　nucleation　on　the　TiAl3　surface.