Low-cost　and　miniaturized　biosensors　are　key　factors　leading　to　the　possibility　of　portable　and　integrated　biomedical　system,　which　play　an　important　role　in　clinical　medicine　and　life　sciences.　Random　lasers　with　simple　structures　provide　opportunities　for　detecting　biomolecules.　Here,　low-cost　biosensors　on　fiber　facet　for　label-free　detecting　biomolecules　are　demonstrated　based　on　a　plasmonic　random　laser.　The　random　laser　is　achieved　resorting　to　a　self-assembled　plasmonic　scattering　structure　of　Ag　nanoparticles　and　polymer　film　on　fiber　facet.　Refractive　index　sensitivity　and　near-surface　sensitivity　of　the　biosensor　are　systematically　studied.　Furthermore,　the　biosensor　is　used　to　detect　IgG　through　specific　binding　to　protein　A,　exhibiting　the　detecting　limit　of　0.68　nM.　It　is　believed　that　this　work　may　promote　the　applications　of　a　plasmonic　random　laser　bio-probe　in　portable　or　integrated　medical　diagnostic　platforms,　and　provide　fundamental　understanding　for　the　life　science.　(C)　2020　Optical　Society　of　America　under　the　terms　of　the　OSA　Open　Access　Publishing　Agreement