The　concrete-filled　steel　tubular　(CFST)　K-joint　was　taken　as　the　research　object,　full-scale　specimen　tests　and　finite-element　(FE)　analysis　of　seven　CFST　K-joints　and　one　steel　tubular　(ST)　K-joint　were　carried　out.　The　accuracy　of　CFST　K-joint　stress　concentration　coefficient　(SCF)　calculation　using　the　existing　K-joint　SCF　formula　was　discussed.　Based　on　the　effect　of　core　concrete　on　the　chord　deformation　mechanism,　the　releasing　coefficient　of　CFST　K-joint　SCF　was　proposed.　According　to　the　relationship　between　releasing　coefficient　and　stripping　arc　length,　the　calculation　method　of　releasing　coefficient　was　established　by　theoretical　derivation.　The　calculation　method　of　CFST　K-joint　SCF　was　then　established　based　on　the　releasing　coefficient　and　ST　K-joint　SCF.　The　obtained　results　show　that　the　maximum　SCF　of　the　K-joint　appears　in　the　position　of　the　intersecting　weld　between　tension　brace　and　chord　near　the　crown　toe　of　the　chord.　The　maximum　SCFs　of　the　CFST　and　ST　K-joints　in　order　are　obtained　as　3.98　and　6.08,　which　indicates　that　the　core　concrete　can　reduce　the　SCF　of　the　CFST　K-joint　by　about　34.5%.　The　existing　methods　for　calculating　the　SCF　of　CFST　and　ST　K-joints　fail　to　fully　consider　the　influence　of　core　concrete　constraints　and　the　coupling　relationship　between　geometric　parameters;　therefore,　the　accuracy　of　CFST　K-joint　SCF　calculation　using　the　existing　K-joint　SCF　calculation　formula　is　low.　By　employing　the　proposed　SCF　calculation　method,　the　calculation　error　of　the　CFST　K-joint　SCF　can　be　reduced　from　58.0%　to　19.6%.