To　analyze　the　reason　why　fatigue　cracking　appeared　on　the　rib　joint　of　a　half-through　concrete　filled　steel　tubular　(CFST)　truss　arch,　finite　element　(FE)　analysis　is　carried　out　by　establishing　the　full-bridge　FE　model　using　the　software　of　MIDAS/CIVIL.　By　studying　the　variation　of　the　stress　amplitude　of　the　arch　rib　joint　under　different　vehicle　loads　and　geometric　parameters　of　the　arch　rib　joint　respectively,　the　influence　of　overloading,　medium　loading　and　unbalanced　loading　on　the　stress　amplitude　is　analyzed.　Furthermore,　the　influence　of　geometric　parameters　of　the　arch　rib　joint　on　the　stress　amplitude　is　also　discussed.　It　is　found　that　the　stress　amplitude　of　the　arch　rib　joint　linearly　increases　with　the　variation　of　overloading　percent,　including　30%,　50%,　100%　and　150%,　respectively,　and　the　maximum　value　of　the　stress　amplitude　reaches　155　MPa.　Besides,　the　stress　amplitude　caused　by　a　BS5400　fatigue　vehicle　model　is　the　maximum　comparing　with　others.　However,　the　value　of　the　stress　amplitude　caused　by　unbalanced　loading　is　1.2　times　as　that　caused　by　medium　loading　under　a　China　550　kN-vehicle　model.　Thus,　overloading　and　unbalanced　loading　lead　to　fatigue　cracking　and　the　unsymmetrical　distribution　of　fatigue　cracks　on　the　arch　rib　joint　of　a　CFST　truss　bridge　respectively.　The　stress　amplitude　of　the　joint　decreases　with　the　increase　of　the　ratio　of　brace　thickness　to　chord　thickness,　but　with　the　increase　of　the　ratio　of　brace　diameter　to　chord　diameter,　chord　diameter　to　thickness　and　brace　diameter　to　thickness,　the　stress　amplitude　increases　first　and　then　decreases.　©　2017,　Engineering　Mechanics　Press.　All　right　reserved.