Abstract: As a kind of rig-rod-like polymer, Poly-p-phenylene benzobisoxazole (PBO) has received great interest because of its excellent mechanical properties and good thermal stability. The use of PBO fibers, however, is limited due to its low sunlight stability. Therefore it is necessary to study the UV aging and UV aging resistance of the fiber．This article reviews the recent research progress of study in the UV aging and UV-aging resistance of PBO fiber. Further more，UV aging process and photo aging mechanism of PBO fiber is also discussed．The aging resistance of PBO fiber can be improved by perfecting the structure of fiber and adding appropriate UV-aging agent. And some methods of PBO fiber chemical modification are introduced in this article.