In　transient　conditions　close　to　the　industrialized　application　situation,　the　removal　of　toluene　was　investigated　with　a　lab-scale　bio-trickling　filter　inoculated　with　pure　bacterial　culture　(Pseudomonas　putida).　The　start-up　process　and　the　ability　of　resisting　different　toluene　loading　in　the　steady　state　on　the　performance　of　the　bio-trickling　filter　were　studied.　The　microstructure　of　biofilm　in　the　filter　was　also　observed.　With　inlet　concentration　range　from　544　to　1044　mg　x　m(-3)　at　the　temperature　ranging　from　17　to　26　degrees　C,　the　removal　efficiency　of　toluene　was　almost　100%　at　the　residence　time　of　54　s　and　43.2　s.　The　maximum　volumetric　removal　loading　of　105.35　g　x　(m3　x　h)(-1)　was　achieved.　The　results　indicate　that　it　was　feasible　to　remove　toluene　by　Pseudomonas　putida　which　had　not　be　acclimated　by　toluene.　In　the　steady　state,　the　bio-trickling　filter　had　a　high　flexibility　for　the　load　change　and　the　removal　efficiency　of　the　reactor　was　not　influenced　by　the　variance　of　residence　time　and　inlet　concentration.　The　rapid　increase　of　biofilm　can　be　controlled　by　adjusting　the　interval　of　nutrition　liquid　accession.　There　were　some　changes　in　bacterial　community,　and　lots　of　micro-pore　existed　in　the　biofilm.　It　was　proved　that　the　absorption　of　the　biofilm　was　an　important　precondition　for　the　biodegradation　of　toluene.