Abstract: In view of the shortcomings of traditional polymeric flocculants, such as their simple structure, high dosage, and easy decomposition to cause secondary pollution, This study used environmentally friendly acrylate （AA）, methylacryloyloxyethyl trimethylammonium chloride （DMC）, and chitosan （CS） to synthesize a novel cationic flocculant. Its treatment efficacy on azo dye wastewater and antibacterial properties was evaluated. A CS-g-PDA terpolymer was prepared via radical polymerization in aqueous solution. Structural characterization was performed using Fourier transform infrared spectroscopy and X-ray diffraction, while surface morphology and pore structure were examined by field-emission scanning electron microscopy and specific surface area analysis. Preparation conditions were optimized through single-factor experiments. The optimized flocculant was applied to treat simulated wastewater containing Congo red, amaranth red, and Acid Orange G （individually or mixed）, and antibacterial activity was tested via the Oxford cup method. The structure characterization shows that the target copolymer has been successfully synthesized, with surface morphology conducive to adsorption and flocculation. Under optimized conditions, the flocculant achieved >90% removal for all three azo dyes and similar efficacy for mixed dyes. The Oxford cup test revealed distinct inhibition zones, indicating antibacterial properties. The CS-g-PDA flocculant overcomes traditional flocculants' shortcomings by combining high dye removal efficiency with antibacterial functionality, making it an environmentally friendly water treatment material with excellent performance.