A　three-dimensional　solid　finite　element　model　was　established　to　carry　out　parametric　analysis　on　the　stress　concentration　factor　of　circular　hollow　section　(CHS)　K-joints　by　the　general　software　of　MSC.MARC.　Based　on　the　existing　results　of　tests　and　finite　element　analysis　of　CHS　K-joints,　deficiency　of　the　formula　adopted　by　the　current　codes　to　calculate　the　stress　concentration　factor　of　CHS　K-joints　was　revealed.　A　method　for　calculating　the　stress　concentration　factor　based　on　CHS　K-joint　stiffness　was　proposed　by　combining　the　theoretical　derivation　and　regression　analysis,　and　the　accuracy　and　feasibility　of　the　calculating　method　was　validated.　It　is　found　that　the　differences　between　the　test　results　and　the　finite　element　analysis　results　in　terms　of　the　maximum　displacement　and　maximum　hot　spot　stress　of　CHS　K-joints　are　less　than　5.11%　and　6.83%,　respectively,　demonstrating　that　the　finite　element　model　has　high　accuracy.　By　comparing　with　the　results　of　finite　element　analysis,　it　is　found　that　there　is　a　coupling　effect　among　the　geometric　parameters　of　CHS　K-joins　in　its　stress　concentration　factor,　as　the　variation　of　one　parameter　generally　leads　to　the　variation　of　other　parameters.　Because　the　current　stress　concentration　factor　calculating　method　of　CHS　K-joints　is　based　on　regression　analysis　according　to　single　geometric　parameter,　it　ignores　the　coupling　effect　caused　by　geometric　parameters　of　the　joints.　Therefore,　it　has　a　small　safety　margin　and　is　not　suitable　to　calculate　the　stress　concentration　factor　of　CHS　K-joints　used　in　bridge　structures.　The　proposed　stress　concentration　factor　calculating　method　based　on　CHS　K-joint　stiffness　can　not　only　consider　the　coupling　effect　caused　by　the　geometric　parameters　of　the　joints,　but　also　improve　the　safety　margin　and　accuracy　of　evaluating　and　calculating　the　stress　concentration　factor　of　CHS　K-joints　used　in　bridge　structures.　©　2020,　Editorial　Office　of　Journal　of　Building　Structures.　All　right　reserved.