We　use　the　two-component　drift-diffusion　model　to　study　the　spin　density　polarization　in　an　organic　semiconductor　system　under　an　external　electric-field.　The　spin-dependent　electrical-conductivity,　the　drift　spin　current　and　the　diffusion　spin　current　in　the　organic　semiconductor　are　self-consistently　derived.　It　is　found　that　the　spin　current　could　be　strongly　influenced　by　the　spin-dependent　electrical-conductivity.　When　the　spin-dependent　conductivity　varies　from　0　to　0.5%,　the　spin　current　presents　a　very　pronounced　change　almost　three　orders　in　magnitude.　The　electric-field　could　effectively　enhance　the　spin-dependent　electrical-conductivity　and　the　spin　current.　Furthermore,　the　spin-dependent　electrical-conductivity　is　position　sensitive,　but　its　position　sensitivity　goes　down　while　electric-field　is　larger　than　about　1　mV/mu　m.　(C)　2008　Elsevier　B.V.　All　rights　reserved.