Spin　injection　in　an　organic　semiconductor　system　under　an　external　electric-field　was　studied　theoretically　by　considering　spin-dependent　conductivity.　The　effect　of　the　spin-dependent　electrical-conductivity　on　the　spin-injection　efficiency　is　self-consistently　derived.　It　is　found　that　the　spin-injection　efficiency　depends　evidently　on　the　spin-dependent　electrical-conductivity.　When　the　spin-injection　efficiency　increases　20%,　the　spin-dependent　electrical-conductivity　increases　nearly　four　orders　of　magnitude　at　T　=　10　K.　With　the　increase　of　external　electric-field,　the　spin-dependent　electrical-conductivity　increases　sharply　and　makes　the　spin-injection　efficiency　increase,　too.　When　the　external　electric-field　varies　from　1　to　10　mv/mu　m,　the　spin-injection　efficiency　increases　almost　10%　at　room　temperature.　It　seems　to　be　significant　to　consider　the　spin-dependent　electrical-conductivity　under　the　external　electric-field　in　spin-injected　organic　system.　(C)　2010　Elsevier　B.V.　All　rights　reserved.