A series of carboxymethyl chitosan (CMC) with 2,4-dihydoxybenzophenone (UV-0) substituent were synthesized by the Mannich reaction of CMC hydrochloride and UV-0 in the solvent of methanol and water. The different molar degree of substitution (MS) was achieved by changing the UV-0 content. The effects of NIS on ultraviolet absorbability, crystallinity, moisture-absorption and -retention property, and photostability were investigated respectively. The obtained products were characterized by means of Fourier transform infrared spectra (FTIR), proton nuclear magnetic resonance spectroscopy (H-1 NMR), X-ray diffraction, and UV spectrophotometer. It was found that the grafted products were water-soluble, and the increased MS values could enhance the moisture-retention property and photostability, while decreased the crystallinity and moisture-absorption property. The ultraviolet absorption peaks became stronger by introducing UV-0 into the CMC backbones.