The　structural　materials　in　nuclear　power　plants　experience　corrosion　under　high　temperature　water　chemistry　environments,　which　could　result　in　serious　safety　issues.　Zinc　injection　to　the　primary　side　chemistry　has　been　demonstrated　to　reduce　corrosion　rate　of　the　structural　materials　and　radiation　dose　rate　by　modifying　the　oxide　film　formed　on　the　structural　materials.　The　purpose　of　this　work　is　to　investigate　the　effect　of　Zn　addition　at　different　concentrations　on　304SS　under　PWR　primary　side　conditions　by　SEM,　GIXRD,　Raman　spectrum,　XPS,　electrochemical　method　and　thermodynamic　calculation.　When　Zn　concentration　is　increased,　the　number　and　size　of　Fe-based　spinel　oxide　particles　in　the　outer　layer　decreases　while　Cr-based　spinel　oxide　in　the　inner　layer　remains　unchanged.　The　corrosion　current　density　of　304SS　and　defect　density　of　the　oxide　film　decrease　with　increasing　Zn　concentration.　These　results　conclude　that　corrosion　resistance　of　304SS　is　enhanced　in　the　presence　of　Zn.　In　addition,　the　thermodynamic　analyses　on　the　spinel　oxides　of　surface　were　performed　and　the　results　are　in　good　agreement　with　the　experimental　observations　presented　in　this　work.