The　laser　welding　of　3　mm　thick　TC4　titanium　alloy/15-5PH　stainless　steel　was　carried　out　with　nickel　aluminum　bronze　(NAB)　as　the　transition　layer.　Effects　of　adding　NAB　transition　layer　on　the　joint　formation,　microstructure　and　mechanical　properties　were　studied.　The　results　show　that　the　laser　welding　of　TC4　titanium　alloy/15-5PH　stainless　steel　with　NAB　transition　layer　can　obtain　a　well-formed　full　penetration　joint.　The　tensile　strength　of　the　joint　is　290　MPa,　and　the　hardness　of　the　interface　layer　on　the　titanium　alloy　side　is　547.8　HV.　The　interface　on　the　titanium　alloy　side　of　the　joint　is　composed　of　three　IMCs　layers　with　different　morphologies.　The　number　of　less　brittle　Cu-Ti　and　Ni-Ti　phases　increases　significantly,　while　the　number　of　highly　brittle　Ti-Fe　phases　decreases　significantly,　indicating　that　the　addition　of　NAB　transition　layer　inhibits　the　formation　of　highly　brittle　Ti-Fe　phases　at　the　interface　of　titanium　alloy　side.　Copyright　©　2022　Transactions　of　the　China　Welding　Institution.　All　rights　reserved.