Recently,　the　application　of　environment-friendly　materials　in　electronic　devices　has　attracted　more　and　more　attention,　and　become　an　important　trend　in　the　future　development　of　electronic　devices.　Hydrogel　as　a　kind　biocompatible　and　biodegradable　material　with　rich　water,　is　ubiquitous　in　biological　system.　For　the　first　time,　we　fabricated　bottom　coupled　organic　synaptic　transistor　using　gelatin　hydrogel　as　the　dielectric　material,　which　exhibited　good　transistor　performance　with　low　operating　voltage.　More　importantly,　some　crucial　synaptic　functions,　such　as　excitatory　postsynaptic　current　(EPSC)/inhibitory　postsynaptic　current　(IPSC),　paired-pulse　facilitation　(PPF)/paired-pulse　depression　(PPD)　and　high-pass　filtering　characteristics,　were　successfully　stimulated　in　our　device.　In　addition,　the　transition　from　sensory　memory　(SM)　to　short-term　memory　(STM)　and　from　STM　to　long-term　memory　(LTM)　based　on　the　multistore　model　in　the　human　brain　was　also　observed　in　our　device.　Moreover,　we　stimulated　the　classical　conditional　Pavlov＇s　dog　experiments　in　the　device.　The　gelatin　hydrogel-gated　synaptic　transistor　proposed　in　this　work　shows　great　potential　in　biocompatible　synaptic　electronics,　which　inspires　a　new　direction　for　building　future　environmental　neuromorphic　electronics.　©　2019　Elsevier　B.V.