Abstract: To investigate the protective effects of Tempol（a nitroxide）on skin photodamage caused by ultraviolet in guinea pigs from the view of pathology. Methods: A total of 36 guinea pigs were divided into 3 groups randomly: nonradiation control, radiation control and Tempol . Except for nonradiation control, other two groups were monitored following radiation with ultraviolet for 14 weeks. Results: The collagen and elastic fibers became thicker，fragmented and disarranged in radiation control group．And the MDA content in radiation control group was significantly higher than in nonradiation and Tempol groups at the same time (P＜0.01). Conclusion: Tempol has a protective effect on skin photodamage caused by ultraviolet.

Key words: Nitroxide, Ultraviolet, Photodamage, Guinea pigs