The　effect　of　KrF　pulsed　excimer　laser　irradiation　on　intrinsic　defects,　ultra-violet　(UV)　emission　and　surface　morphology　of　ZnO　thin　films　was　investigated,　and　also　the　origin　of　room　temperature　UV　emission　was　discussed　in　detail.　It　was　found　that,　the　Krf　laser　can　break　the　Zn-O　bonds;　therefore,　the　concentration　of　V-o　(or　Zn)　defects　increases,　leading　to　the　decrease　of　resistivity　and　increase　of　carrier　concentration.　By　adjusting　the　laser　energy　densities,　the　donor　defect　concentration　can　be　controlled　in　a　wide　range　Simultaneously,　under　the　heat　of　laser,　the　melting　grains　connect　with　each　other,　resulting　in　the　great　decrease　of　surface　roughness.　Room　temperature　UV　emission　of　ZnO　film　is　composed　of　contribution　from　free-exciton　(FX)　recombination　and　its　longitudinal-optical　phonon　replica　(FX-LO),　the　defect　density　determines　the　relative　strengths　of　FX　to　FX-LO　emission　intensities,　which　strongly　affect　the　peak　position　and　intensity　of　UV　emission　of　ZnO　film　This　investigation　indicates　that　the　laser　irradiation　is　an　effective　technique　to　modulate　the　exciton　emission　by　controlling　the　defect　density,　which　is　important　for　the　application　of　high　performance　of　UV　emitting　optoelectronic　devices.