To　quantify　the　Li　diffusion　behavior　in　nanocrystalline　anode　materials　for　lithium-ion　batteries　(LIBs),　a　hybrid　model　of　the　first　principles　calculation　and　diffusion　kinetics　was　developed.　The　dependence　of　the　Li　diffusion　on　the　electronic　structure,　solute　concentration,　grain　size　and　temperature　was　described　for　the　nanocrystalline　Li-Si　system.　In　contrast　to　conventional　polycrystalline　materials　in　which　the　activation　barrier　for　Li　diffusion　decreases　with　the　increase　of　concentration　before　amorphization,　there　exists　a　coordination　effect　of　the　solute　concentration　and　grain　size　on　the　Li　diffusion　in　nanocrystalline　materials.　A　maximum　diffusion　coefficient　can　be　obtained　in　the　nanocrystalline　Li-Si　by　a　combination　of　the　concentration　and　grain　size,　which　is　increased　by　two　orders　of　magnitude　from　that　in　the　coarse-grained　counterpart.　The　present　work　advanced　the　understanding　of　the　Li　diffusion　mechanisms　during　lithiation/delithiation　of　LIBs　and　may　facilitate　the　development　of　nanocrystalline　anode　materials.