The　absorption　and　emission　spectra　of　the　wurtzite　Mn-doped　GaN　were　calculated　with　cluster　models.　The　predicted　lattice　parameters　become　slightly　larger　than　those　of　undoped　cluster.　The　average　bond　length　of　Mn-N　is　longer　than　that　of　Go-N.　Spin　density　shows　that　one　Mn　atom　in　these　clusters　has　four　single　electrons　with　the　same　direction　of　the　spin　polarity　The　new　energy　level　with　light　Mn-doping　appears　at　1.37　eV　above　the　valance　band.　The　absorption　spectra　of　Mn-doped　GaN　cover　the　visible　light　region.　The　calculated　emission　spectra　show　that　the　green　luminescence　of　GaN　material　in　experiment　did　not　result　from　Mn　dopant.　With　the　increase　of　Mn　doping,　the　emission　intensity　of　yellow　or　blue　band　increases　to　different　extent　and　the　band-to-band　emission　band　shows　red　shift　from　peak　at　3.34　to　3.24　eV.