The B-F codoped nano-TiO2 particles powders were prepared by the sol-gel method. The PS/B-F co-doped nano-TiO2 composite was synthesized with in situ polymerization. The films of PS/SBS/B-F co-doped nano-TiO2 composites were prepared by the hot-pressing machine, and the accelerated photodegradation of films were investigated with a 1000W xenon lamp. The surface morphology and Tg of the films in the process of degradation were detected by SEM and DSC. Results showed that the Tg of PS/SBS/B-F codoped nano-TiO2 composite is the lowest of all samples. More and large holes were observed in the surface of PS/SBS/B-F codoped nano-TiO2 composite film.