Green-synthesized gel materials can efficiently absorb and remove organic dyes from wastewater. This investigation designed and synthesized a novel modification method of sodium alginate gel beads based on the protein glycosylation reaction (Maillard reaction) using green chemistry principles. The prepared gel beads were subsequently applied to examine their efficacy in adsorbing the organic dye methylene blue. The adsorption process and mechanism were characterized and analyzed. At an adsorption equilibrium of 300 K, the adsorption value can reach 908 mg/g. The dry casein glycosylated gel beads synthesized in this study demonstrate the potential for further development as a novel adsorbent for organic dyes in wastewater.