Quaternized Carboxymethyl Chitosan (QCMC) combines the potent antibacterial properties of quaternary ammonium salts with the superior hydrophilic solubility of carboxymethyl groups, making it widely applied in biomedicine for advanced wound dressings, hemostatic hydrogels, ophthalmic sustained-release formulations, anti-adhesion barriers, and non-viral gene/drug delivery vectors. In cosmetics and personal care, it functions as a mild antibacterial agent, film-forming moisturizer, and hair conditioning enhancer. Additionally, QCMC is utilized as a plant immunity inducer and biopesticide enhancer in agriculture, as well as a heavy metal chelator, wastewater flocculant, and wet-strength agent in papermaking and environmental engineering.