To　clarify　the　effect　of　the　laser-induced　plume　on　weld　penetration　during　high-power　fiber　laser　welding,　this　paper　investigates　the　change　in　weld　penetration,　plume　behavior　and　temperature,　particles　present　in　the　plume,　and　the　attenuation　of　the　horizontal　probe　laser.　Results　show　that　the　weld　penetration　had　an　improvement　of　about　20%　as　the　plume　was　blown　away　by　using　a　supersonic　cross　jet.　The　plume　temperature　at　a　height　of　5mm　was　approximately　5078　K.　The　weld　penetration,　plume　temperature,　and　plume　attenuation　to　a　probe　laser　decreased　as　plume　height　increased.　A　plume　height　of　approximately　80mm　resulted　in　a　shape　similar　to　that　of　a　focused　laser　beam;　a　cone　of　white　smoke　composed　of　numerous　particles　appeared　around　the　plume.　Calculated　and　measured　results　indicate　that　the　interaction　of　laser　particles　in　the　plume　accounts　for　the　primary　impact　on　laser-plume　interaction.　It　is　found　that,　if　the　plume　height　increases,　the　weld　penetration　decreases　correspondingly　due　to　the　increasing　attenuation　of　the　high-power　fiber　laser　beam　by　the　particles　in　the　plume.　(C)　2016　Laser　Institute　of　America.