To　study　the　fatigue　performance　of　concrete-filled　steel　tubular　K-joint　(CFST　K-joint)　with　internal　studs,　fatigue　tests　on　CFST　K-joint　without　internal　studs,　CFST　K-joint　with　array　arrangement　internal　studs　(CFST　KSA-joint),　and　CFST　K-joint　with　circular　arrangement　internal　studs　(CFST　KSC-joint)　were　conducted.　The　finite　element　models　of　CFST　K-joints　with　studs　were　established.　The　hot-spot　stress　distributions,　fatigue　crack　growth　processes,　and　fatigue　failure　modes　of　the　joints　mentioned　above　were　comparatively　studied.　The　study　showed　that　the　maximum　hot-spot　stress　of　the　CFST　K-　and　KSA-joints　appeared　at　the　crown　toe,　while　that　of　the　CFST　KSC-joint　occured　at　the　position　of　45°.　As　compared　with　CFST　K-joints,　the　CFST　KSA-　and　KSC-joint　specimens　had　34%　and　12%　reductions　in　hot-spot　stress,　respectively.　At　the　location　of　the　internal　studs,　the　hot-spot　stress　decrease　significantly.　By　reducing　the　chord　deformation　and　peeling　arc　length,　the　internal　studs　reduce　the　hot　spot　stress　and　increase　the　fatigue　life.　The　fatigue　life　of　the　CFST　KSA-joint　specimen　with　array　internal　studs　was　101%　higher　than　that　of　the　CFST　K-joint　specimen.　By　applying　the　circular　internal　studs,　the　fatigue　life　of　the　CFST　KSC-joint　specimen　was　97%　higher　than　the　CFST　KSA-joint　specimen　with　array　internal　studs.　The　internal　studs　delay　the　occurrence　of　fatigue　cracks,　and　change　the　propagation　path　of　fatigue　cracks　along　the　length　of　intersecting　welds　into　the　direction　of　steel　tube　wall　thickness,　therefore,　improving　the　fatigue　life　of　K-joints.　©　2022　Elsevier　Ltd