Humidity　sensing　plays　an　important　role　in　the　professional　field　and　our　daily　life,　such　as　chemical　preparation　process,　environmental　monitoring,　and　food　storage.　Herein,　a　wearable　humidity　sensor　is　designed　based　on　a　flexible　plasmonic　random　laser.　The　random　laser-based　humidity　sensor　is　fabricated　by　transferring　an　ultrathin　light-emitting　polymer　membrane　doped　with　silver　nanoparticles　onto　the　humidity-sensitive　PEDOT:PSS　film.　Under　optical　pumping,　random　lasing　with　low-threshold　is　achieved,　assisted　by　the　strong　plasmonic　feedback　of　the　silver　nanoparticles.　The　random　laser-based　humidity　sensor　exhibits　a　good　linear　response　with　a　coefficient　of　0.997.　Comparing　with　the　emission　intensity　at　initial　relative　humidity　(RH)　(34.8%),　the　peak　intensity　increases　5.5　times　at　an　RH　value　of　93.5%.　This　phenomenon　mainly　results　from　the　ambient,　humidity-sensitive　relative　refractive　index　difference　between　polymer　membrane　and　PEDOT:PSS　film.　The　random　laser-based　humidity　sensor　is　flexible　and　nontoxic,　which　can　be　transplanted　easily　to　achieve　wearable　laser　devices.