The　simultaneous　observation　of　both　plume　morphology　and　particle　in　plume　is　crucial　for　characterizing　the　plume　dynamic　behavior　with　the　particle　signals　during　fiber　laser　keyhole　welding.　In　this　study,　synchronous　triggering　of　the　photodetector　and　the　particle　in-situ　measurement　system　facilitated　the　simultaneous　observation　of　both　plume　morphology　and　particle　within　the　fiber　laser　beam,　as　well　as　the　relationship　between　the　plume＇s　visual　image　and　the　optoelectronic　signal.　In　the　early　stages　of　fiber　laser　welding,　optoelectronic　signals　and　particle　signals　are　generated　nearly　simultaneously.　During　the　welding　process,　the　plume　can　be　categorized　into　a　bottom　oscillating　section　and　a　narrow　section　resembling　the　focusing　pattern　of　the　fiber　laser　beam.　Notably,　when　the　bottom　plume　oscillates　in　the　direction　of　the　fiber　laser　beam,　the　maximal　amplitude　of　the　particle　signals　is　observed.　This　characteristic　is　independent　of　various　parameters,　including　laser　power,　welding　speed,　and　the　defocus　distance.　When　the　bottom　plume　swings　toward　the　fiber　laser　beam,　the　particles　carried　by　the　plume　into　the　focused　beam　contribute　to　the　maximal　signal　amplitude.　This　feature　can　be　utilized　to　establish　a　correspondence　between　particle　signals　and　the　oscillating　behavior　of　the　plume.　©　2025　Elsevier　Ltd