Biodegradable　and　environmentally　friendly　artificial　synapse　devices　are　essential　for　the　future　development　of　neuromorphic　computing.　The　emergence　of　synaptic　transistors　based　on　biocompatible　polymer　materials　provides　an　ideal　approach　to　achieve　green　electronics.　However,　modulating　the　synaptic　properties　in　a　wide　range　in　a　fixed　biocompatible　synaptic　transistor　is　still　challengeable,　while　it　is　vitally　important　for　improving　the　adaptability　of　the　synaptic　device　to　achieve　neuro-prosthetics　in　the　future.　Here,　we　reported　the　regulation　of　the　synaptic　behavior　of　biocompatible　synaptic　transistor　through　ion-doping,　which　allows　to　adjusting　the　response　of　the　synaptic　device　according　to　a　specific　function.　The　ions　doped　into　the　insulating　layer　strengthen　the　formation　of　electric　double　layers　(EDLs),　which　enables　a　remarkable　regulation　effect　on　post-synaptic　current.　Moreover,　basic　synaptic　properties,　including　excitatory/inhibitory　post-synaptic　current　(EPCS/IPSC),　paired-pulse　facilitation/depression　(PPF/PPD),　short-term/long-term　memory　(STM/LTM)　are　successfully　demonstrated.　In　addition,　high-pass　and　low-pass　filtering　functions　are　also　implemented　in　a　single　synaptic　device,　indicating　that　the　synapse　attenuation　can　be　effectively　transformed　according　to　the　needs　of　the　function.　More　importantly,　this　is　the　first　work　to　demonstrate　that　the　accuracy　of　pattern　recognition　of　synaptic　transistors,　an　important　indicator　of　neuromorphic　calculations,　can　be　significantly　improved　via　ion　doping　(as　high　as　75.96%　relative　to　undoped　devices　of　41.68%).　Our　research　provides　a　feasible　strategy　for　precisely　controlling　synaptic　behaviors,　which　has　a　profound　impact　on　improving　the　adaptability　of　artificial　synaptic　devices　in　the　field　of　neuromorphic　computing.