A water-soluble polymeric UV-absorber with polyvinylamine as backbone and benzotriazole type UV absorber as anti-UV functional group was synthesized by grafting brominated (2-acetoxy-5-methylphenyl)-2H-benzotriazole onto polyvinylamine. The intermediates and synthesized polymeric UV absorber were characterized by 1H NMR, MS, IR and UV spectroscopy. The finishing properties of the polymeric UV absorber on cotton were investigated to show good UV protection property and wash fastness.