The　site　occupancy　dependence　of　12　transition　metal　elements　on　Ti/Al　ratio　and　temperature　usually　used　for　the　alloying　of　L10-TiAl　were　studied　by　thermodynamic　model　and　first-principles　calculation　using　a　general　three　sublattice　model.　Ti　and　Al　in　the　alloy　with　2%(atom　fraction)　alloying　elements　had　very　strong　site　preferences　in　the　range　of　Ti/Al　ratio　from　0.6　to　1.4.　The　transition　metals　could　be　classified　into　two　groups　when　the　Ti/Al　ratio　changed　from　0.6　to　1.4　at　1173　K.　The　site　occupancies　of　V,　Ta,　Mo,　Mn,　Cr,　Zn　and　W　changed　from　Ti　sublattice　to　Al　sublattice　around　Ti/Al=1　and　the　site　occupancies　of　Zr,　Nb,　Tc,　Co　and　Ag　did　not　change　a　lot.　The　transition　metals　could　also　be　fall　into　two　groups　when　the　temperature　changed　from　200　K　to　2000　K　in　Ti0.49Al0.49M0.02　with　Ti/Al=1.　The　site　occupancies　of　V,　Ta,　Mo,　Tc,　Co,　Mn,　Cr,　Zn　and　W　changed　from　disorder　to　obvious　site　preferences,　and　the　site　occupancies　of　Zr,　Nb　and　Ag　did　not　change　much.　In　contrast,　the　Ti/Al　ratio　had　more　effect　than　the　temperature　on　the　site　occupancies　of　transition　metals　in　L10-TiAl.　The　present　predictions　agreed　well　with　the　previous　reports　from　both　experimental　and　theoretical　studies　in　the　literature.