Polyimide　(PI)　was　used　as　the　substrate　of　flexible　organic　thin　film　transistor　(OTFT),　via　adding　strontium　barium　titanate　(BST)　nanoparticles　to　improve　the　capacitance　of　PVP　polymer　gate　dielectric　layer.　By　using　polymethyl　methacrylate　(PMMA)　to　modify　the　dielectric　layer,　the　quality　and　performance　of　dielectric　layer　film　was　improved.　Meanwhile　the　threshold　voltage　of　flexible　OTFT　was　reduced,　as　well　as　the　current　switch　ratio　and　mobility　increased.　The　test　results　show　that　the　optimized　flexible　OTFT　threshold　voltage　is　-2.5　V.　The　current　switch　ratio　is　more　than　104,　and　the　mobility　is　0.0703　cm2/(V•s).　The　device　can　still　work　normally　under　the　bending　radius　of　3　mm,　while　the　current　switch　ratio　maintains　at　104　grade.　©　2019,　Chinese　Ceramic　Society.　All　right　reserved.