First-principles　calculation　is　a　quite　powerful　tool　for　explaining　experimental　phenomena　and　predicting　the　properties　of　new　materials.　Based　on　the　first-principles　calculation　within　the　density　functional　theory,　the　energetic　stabilities　and　electronic　properties　of　Mg　and　Si　doped　GaN/AlN　superlattices　with　wurtzite　and　zinc-blende　structures　are　investigated.　The　results　show　that　there　is　no　variation　in　formation　energy　if　the　doping　position　is　changed　when　the　impurities　are　doped　in　the　well　(GaN)　region,　and　the　same　situation　also　happens　in　the　barriers　(AlN)　region.　Thus　it　is　equivalent　for　dopants　to　replace　Ga　atoms　in　the　cation　site　of　wells　or　Al　atoms　in　the　cation　site　of　barrers.　However,　the　formation　energies　of　these　dopants　in　the　well　region　and　the　barrier　region　are　different.　Compared　with　the　formation　energy　in　the　barrier　region,　it　is　much　lower　in　the　well　region.　That　is　to　say,　the　impurities　in　the　cation　site　(Mg-Ga,　Mg-Al,　Si-Ga　and　Si-Al)　present　lower　formation　energies　in　the　wells　of　GaN/AlN　SLs　with　wurtzite　and　zinc-blende　structures.　In　addition,　the　impurities　in　zinc-blende　GaN/AlN　superlattices　present　lower　formation　energy　than　in　the　wurtzite　structure.　The　negative　formation　energy　illustrates　that　the　defects　are　spontaneously　formed　if　Mg-atom　is　mixed　into　the　wells　of　the　zinc-blende　structure.　Therefore,　in　experiment,　for　the　zinc-blende　superlattice　structure,　preparing　p-type　semiconductor　needs　less　energy　than　preparing　n-type　semiconductor.　And　for　the　wurtzite　superlattice　structure,　preparing　p-type　semiconductor　needs　the　same　energy　as　preparing　n-type　semiconductor.　Furthermore,　the　relationships　between　the　distribution　of　the　electronic　states　and　their　structures　are　analyzed.　It　is　found　that　the　different　kinds　of　dopants　lead　to　different　band　bendings,　owing　to　the　modified　polarization　fields.　The　spatial　distributions　of　electrons　and　holes,　plotted　by　the　partial　charge　densities,　reveal　that　electrons　and　holes　experience　redistributions　by　Si　or　Mg　dopants　in　different　phases.　The　band　gap　of　doped　GaN/AlN　superlattice　decreases　and　the　projected　density　of　states　also　accounts　for　the　change　of　defect　formation　energy.　The　calculated　results　provide　a　new　reference　for　the　fabrication　of　modulation-doping　GaN/AlN　SL　under　desired　control,　which　could　be　considered　to　control　phase.