The invention relates to a method to prepare a benzotriazole ultraviolet-absorbing agent via a catalytic hydrogen transfer process. The method includes: before hydrogen transfer reaction, refining thereaction material an azobenzene compound, fully removing impurities that disturb the hydrogen transfer reaction to obtain purity of 99% and above, and performing hydrogen transfer reaction. The refining of the material ensures smoothness for the subsequent hydrogen transfer reaction, and the benzotriazole ultraviolet-absorbing agent of high yield and high purity can be obtained; in addition, themethod has significantly reduced usage of quinone catalysts, is green and low in cost and is suitable for industrial production routes.