In　a　1250-MW　pressurized　water　reactor　(PWR),　coolant　is　injected　into　the　reactor　vessel　under　accident　conditions　through　the　method　of　direct　injection,　which　is　the　most　important　function　of　the　emergency　core　cooling　system.　Since　the　problem　has　been　found　that　safety　injection　start-up　will　have　a　significant　thermal　effect　on　the　reactor＇s　internal　system,　a　confirmatory　study　of　an　improved　structure　is　required　in　the　initial　design　stage.　In　this　paper,　the　heat　transfer　and　flow　characteristics　of　the　core　barrel,　the　neutron　shielding　panels,　and　the　radiation　surveillance　capsules　are　investigated　by　a　scaled　experiment　combined　with　a　numerical　method　to　obtain　the　distribution　of　the　wall　temperature　and　the　convective　heat　transfer　coefficient　on　the　outer　wall　of　the　reactor　internals　under　different　injection　conditions.　In　addition,　potentially　dangerous　parts　have　been　pointed　out,　and　dimensionless　correlations　are　fitted　to　describe　the　heat　transfer　laws　of　key　parts　of　reactor　internals　for　use　in　reactor　design.　This　research　fills　in　the　gaps　in　the　study　of　heat　transfer　under　direct　injection　of　the　reactor　internals　in　a　PWR,　providing　support　for　the　safety　of　the　reactor　structure.