Exploring　brain-inspired　synaptic　devices　has　recently　become　a　new　focus　of　research　in　nanoelectronic　communities.　In　this　emerging　field,　incorporating　2D　materials　into　three-terminal　synaptic　transistors　has　brought　various　advantages.　However,　achieving　a　stable　and　long-term　weight-modulation　in　these　synaptic　transistors,　which　are　typically　based　on　interface　charge　storage,　is　still　a　challenge　due　to　the　nature　of　their　spontaneous　relaxation.　The　application　of　an　atomically　thin　fluorographene　layer　into　the　synaptic　junction　region　suppresses　this　issue　and　improves　the　efficiency,　tunability,　and　symmetry　of　the　synaptic　plasticity　as　well　as　establishing　a　stable　weight-regulation　paradigm.　These　unique　properties　can　be　attributed　to　the　dipolar　rotation　of　C-F　in　fluorographene.　To　obtain　a　better　physical　understanding,　a　vacancy-dependent　C-F　dipolar　rotation　model　is　proposed　and　supported　by　hysteresis　analysis　and　density　functional　theory　calculations.　As　proposed　and　demonstrated,　the　unique　fluorographene-based　synaptic　transistor　may　be　a　promising　building　block　for　constructing　efficient　neuromorphic　computing　hardware.