The objective of this study is to examine the feasibility of using visible light to form gels from polysaccharide precursors. Hydrogel formation by visible light irradiation would be very beneficial because visible light is a benign light source and ready available when compared with other light sources such as UV. Dextran-methacylate was synthesized and photocrosslinked using (-)-riboflavin as a photoinitiator and L-arginine as a co-initiator under the visible light. The effect of various concentrations of (-)-riboflavin and L-arginine on the photocrosslinking of dextran-methacrylate hydrogel was investigated. The fabricated hydrogel was characterized by FT-IR and SEM. The photoinitiator [(-)-riboflavin] and co-initiator (L-arginine) as well as dextran precursor are completely biocompatible. The optimum condition for the biocompatible dextran-based hydrogel formation under the harmless light source (visible light) was elucidated in this study. In general, the (-)-riboflavin, 0.01-0.5 %, and L-arginine, 5-20 % of the weight of dextran-methacrylate were the best condition in forming dextran-based hydrogels under the visible light. The three-dimensional hydrogel structure was verified by SEM morphology of swollen hydrogels. Photocrosslinking under the visible light source would enlarge the applications of this type of photocrosslinking in the biomedical area (e.g., eyes or other light-sensitive organs).