The antioxidant activity of polyphenol from Cortex Mori (CMP) was examined by 2,2’-azinobis-(3-ethylbenzthiazoline-6-sulphonate (ABTS) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging assays. Fibroblasts HS68 cells were induced by ultraviolet (UV) irradiation to establish the photoaging model. Cell proliferation was investigated using a methyl thiazolyl tetrazolium (MTT) assay. The content of procollagen typeⅠprotein (PIP) in cells was measured by enzyme-linked immunosorbent assay (ELISA). The matrix metalloproteinase-1 (MMP-1) and PIP mRNA expressi-ons were detected by qRT-PCR. CMP exhibited significant antioxi-dant activity in ABTS, DPPH free radical scavenging assays, with IC₅₀ values of 1.49, 8.94 μg/mL, respectively. The IC₅₀ values of butyl hydroxy anisd (BHA) against ABTS, DPPH radicals were 11.25, 11.03 μg/mL, respectively. The results showed that CMP had stronger scavenging effect on free radicals, and its clearance rate was higher than that of BHA. Compared with the UV group, CMP not only significantly enhanced the fibroblasts proliferation (P<0.05), but also dose-dependently increased the content of PIP (P<0.05). At the same time, CMP down-regulated the MMP-1 mRNA level, and promoted the mRNA expression of PIP (P<0.05). To conclude, polyphenol from Cortex Mori could repair fibroblasts against UV-induced photoaging, and its mechanism may be related to its scavenging effect on free radicals, the inhibition of the expression of MMP-1, and the regulation of the synthesis of PIP.