Effects　of　Co　concentration　on　the　properties　of　ZnSe:Co　films　were　investigated.　The　amorphous　and　crystalline　(ZnSe)(1-x):Co-x　(x　=　=0.1,　0.3,　0.5)　thin　films　were　grown　on　sapphire　(Al2O3)　substrates　with　temperature　of　25　degrees　C　and　800　degrees　C　respectively　by　pulsed　laser　deposition.　The　X-ray　diffraction　analyses　indicate　that,　with　increasing　Co　concentration,　the　average　grain　size　decrease　whereas　the　microstrain　and　dislocation　density　increase.　Meanwhile,　the　further　investigation　for　crystalline　thin　films　shows　that　the　crystalline　phase　transform　from　single　cubic　zinc　blende　structure　to　a　mixture　structure　containing　a　small　amount　of　hexagonal　wurtzite　phase.　The　Raman　spectra　and　X-ray　photoelectron　spectroscopy　reveal　that　the　Co　atoms　were　incorporated　into　ZnSe　lattice　and　the　samples　reached　an　overdoping　state　when　the　x　value　surpassed　0.3.　With　increasing　Co　concentration,　the　average　transmittance　of　films　decreased　due　to　the　Co　impurities　un-incorporating　into　ZnSe　lattice.　Meanwhile,　the　band　gap　E-g　values　of　films　increased　from　3.17　eV　to　3.50　eV　for　T-S　=　=25　degrees　C　and　from　2.86　eV　to　3.34　eV　for　T-S　=　=800　degrees　C.　The　large　E-g　values　with　regard　to　that　of　undoped　bulk　ZnSe　(similar　to　2.7　eV)　can　be　attributed　to　the　Co　doping　and　quantum　confinement　effect.　Moreover,　the　refractive　index　of　the　films　increased　by　improving　Co　concentration.　The　dispersion　energy　E-d,　oscillator　energy　E-o,　static　refractive　index　n(0),　static　dielectric　constant　epsilon(0),　oscillator　strength　S-o　and　oscillator　wavelength　lambda(o)　are　analyzed　by　a　single　oscillator　model.　All　these　parameters　were　found　to　be　dependent　upon　the　Co　concentration　in　the　(ZnSe)(1-x):Co-x　thin　films.