Porous　media　model　in　Fluent　code,　coupled　with　two-phase　mixture　flow　model,　resistance　model　of　tubes　and　heat　transfer　model　through　tubes,　is　employed　to　develop　a　steam　generator　thermohydraulics　analysis　code　STAF　(Steam　generator　Thermohydraulics　Analysis　code　based　on　Fluent).　In　this　code,　the　heat　transfer　from　primary　to　secondary　side　is　calculated　three-dimensionally　during　iteration.　The　localized　velocity,　temperature,　enthalpy,　quality　and　void　fraction　in　steam　generator　can　be　obtained　by　this　code.　STAF　is　validated　in　two　ways.　First,　STAF　is　used　to　calculate　the　thermal-hydraulic　parameters　in　steam　generator　of　AP　1000.　The　calculated　results　are　compared　with　designed　values　to　prove　that　the　coupled　heat　transfer　calculation　in　STAF　is　accurate.　Second,　STAF　is　employed　to　simulate　the　FRIGG　test　to　validate　the　localized　parameter　calculation　performance　by　comparing　the　calculated　localized　void　fraction　with　test　values.　(C)　2016　Elsevier　B.V.　All　rights　reserved.