Amorphous　and　crystalline　Zn1-xCoxS　(x　=　0.1,　0.3,　0.5)　thin　films　were　grown　on　sapphire　(Al2O3)　substrates　by　pulsed　laser　deposition　at　substrate　temperature　of　25　degrees　C　and　800　degrees　C,　respectively.　The　X-ray　diffraction　results　show　that　the　crystalline　film　has　a　cubic　zinc　blende　structure　and　the　crystalline　quality　decreased　with　increasing　Co-doping　concentration.　The　X-ray　diffraction　and　X-ray　photoelectron　spectroscopy　spectra　reveal　that　the　samples　reached　an　overdoping　state　at　Co-doping　concentration　of　x　=　0.5.　The　absorbance　of　films　increases　and　the　absorption　edge　shifts　to　longer　wave　length　direction　with　increasing　Co-doping　concentration.　The　redshift　of　the　band　gap　energy　depends　on　the　Co　composition　associating　with　the　Urbach　energy.　Furthermore,　the　refractive　index　and　dielectric　constant　increase　with　increasing　Co-doping　concentration.　The　dispersion　parameters,　such　as　dispersion　energy　(E-d),　oscillator　energy　(E-o),　static　refractive　index　(n(0)),　static　dielectric　constant　(epsilon(0)),　interband　transition　strength　moments　(M-1　and　M-3),　oscillator　strength　S-o　and　oscillator　wavelength　lambda(o),　have　been　analyzed　by　Wemple-DiDomenico　single　oscillator　model.　All　these　parameters　were　found　to　be　dependent　upon　the　Co-doping　concentration　in　the　Zn1-xCoxS　thin　films.