Single-phase　ultrafine　nanocrystalline　Li2C2　alloy　was　prepared　using　a　simple　and　efficient　technique　that　combines　the　ball　milling　process　and　spark　plasma　sintering.　The　crystal　structure　of　the　nanocrystalline　Li2C2　alloy　was　constructed　by　the　Rietveld　refinement　based　on　the　X-ray　diffraction　pattern　of　the　prepared　nanocrystalline　sample.　Furthermore,　the　phase　stability　in　the　nanocrystalline　Li2C2　alloy　was　quantitatively　studied　using　the　developed　thermodynamic　model　for　the　nanocrystalline　alloys.　It　has　been　found　that　in　a　certain　low　temperature　range,　the　beta-Li2C2,　which　is　a　metastable　phase　in　the　coarse-grained　polycrystalline　system,　can　be　stabilized　due　to　the　nanograin　size　effect.　(C)　2012　Elsevier　B.V.　All　rights　reserved.