Developing memristors with both light-regulated resistive switching characteristic and optronic synaptic behavior is of great significance for next-generation artificial visual applications. Herein, Cu2ZnSn(S,Se)4 (CZTSSe)-based synaptic memristor is designed and its visible light-modulated resistive switching characteristics, especially the photonic synaptic behaviors, are detailedly investigated. For such Ag/CZTSSe/Mo memristor, not only its Set/Reset switching voltage and RHRS/RLRS ratio can be well regulated by visible light, either the wavelength (470 ∼ 655 nm) or intensity (40 ∼ 110 mW/cm2), but also its photonic synaptic behavior like “learning-forgetting” can be achieved and modulated by light stimuli. The results are of significance for designing artificial photonic synaptic devices in neuromorphic vision application.