Enormous　synaptic　devices　are　required　to　build　a　parallel,　precise,　and　efficient　neural　computing　system.　To　further　improve　the　energy　efficiency　of　neuromorphic　computing,　a　single　high-density　synaptic　(HDS)　device　with　multiple　nonvolatile　synaptic　states　is　suggested　to　reduce　the　number　of　synaptic　devices　in　the　neural　network,　although　such　a　powerful　synaptic　device　is　rarely　demonstrated.　Here,　a　photoisomerism　material,　namely,　diarylethene,　whose　energy　level　varies　with　the　wavelength　of　illumination　is　first　introduced　to　construct　a　powerful　HDS　device.　The　multiple　synaptic　states　of　the　HDS　device　are　intrinsically　converted　under　UV-vis　regulation　and　remain　nonvolatile　after　the　removal　of　illumination.　More　importantly,　the　conversion　is　reconfigurable　and　reversible　under　different　light　conditions,　and　the　synaptic　characteristics　are　comprehensively　mimicked　in　each　state.　Finally,　compared　with　a　two-layer　multilayer　perceptron　(MLP)　architecture　based　on　static　synaptic　devices,　the　HDS　device-based　architecture　reduces　the　device　number　by　16　times　to　achieve　a　minimalist　neural　computing　structure.　The　invention　of　the　HDS　device　opens　up　a　revolutionary　paradigm　for　the　establishment　of　a　brain-like　network.　©　2021　American　Chemical　Society.