With p-toluenesulfonic acid as acidic catalyst, employing resorcinol and ethylacetoacetate, 7-hydroxy-4-methyl coumarin, which owned UV absorption properties, was synthesized through dehydration condensation reaction. A coumarin light stabilizer which contains the structure of benzophenone was synthesized through joining the 7-hydroxy-4-methyl coumarin, ultraviolet absorber 2,4-dihydroxy-benzophenone and taurine in the same molecule by cyanuric chloride. The molecular structures were characterized by IR spectra and 1HNMR; optical properties were measured by UV spectra and fluorescence spectra, besides the effect of anti-UV aging was evaluated as the surface sizing agent on handsheet of high yield pulps by using the ultraviolet aging apparatus. The results showed that, with the optimal dosage, the coumarin light stabilizer was superior to reactive UV-Stabilizer or the conventional fluorescent brighteners on the effect of anti-UV aging, and the declining brightness of handsheet relative to them were 2.14%ISO and 3.13%ISO respectively.