A modified benzophenone UV-absorber containing reactive group (4-(4,6-dichloro-1,3,5-triazin-2-yloxy)-2-hydroxyphenyl)phenyl)methanone (UV-DTHM) has been prepared in good yield from the nucleophilic substitution reaction of 2,4-dihydroxy benzophenone with 2,4,6-trichlorotriazine, catalyzed by 1.3 equiv. NaOH. The most favorable reaction conditions (the catalyst dosage, the mole ratio of the reactants, and reactive time) were selected. The compound was characterized by IR spectroscopy, 1H NMR, 13C NMR, mass spectrometry, elemental analysis, and single crystal X-ray diffraction. The crystal monoclinic, space group C c with the unit cell parameters a = 3.987(2), b = 30.688(16), c = 12.423(6) Å and α = 90.00, β = 92.117(15), γ = 90.00º, Z = 4, R = 0.0620. wR(F2) = 0.1589. The crystal structure reveals that 2,4,6-trichlorotriazine is boned to 4-seat hydroxyl of 2,4-dihydroxy benzophenone and a intramolecular hydrogen bond is formed with hydrogen of 2-hydroxyl and oxygen of carbonyl group. Moreover, thermogravimetric analysis (TGA) of UV-DTHM was studied, showing two distinct endothermic peaks at temperatures of 281.5 and 358.5 °C. The molar absorption coefficient of UV-DTHM is 1.6 × 104 and 6.3 × 103 at 268 and 330 nm, respectively, and shows excellent ultraviolet absorption property.