Abstract: The present study aimed to explore the role of curcumin(Cur) which is a pharmacologically natural compound from the Curcuma longa herb, in the protection against UVA-induced photo aging and photocarcinogenesis in cultured fibroblast cells, and the underlying molecular mechanisms were investigated. MTT assay, flow cytometic were used to measure the cell viability and apoptotic rate. The values of UVA-induced ROS and activities of anti oxidative defense enzymes, including GSH, SOD and CAT were evaluated. The proteins involving in ER stress, the apoptotic pathway, inflammation and the collagen synthesis pathway were analyzed by western blotting. Results showed that Cur can prevent the cells from UVA-damage, efficiently decrease the accumulation of ROS and restore the activities of antioxidant defense enzymes. Moreover, Cur could attenuate UVA-induced ER stress, inflammation and apoptotic signaling by reducing the URP78, CHOP, NF-κB and caspase 3 respectively, while increasing Bcl-2. Furthermore, Cur prevent the collagen degradation by decreasing the expression of MMP1 and MMP3, meanwhile, enhance the collagen synthesis by recovering the activity of TGF-β and Smad2/3 and inhibiting that of Smad7. Overall, our results strongly demonstrated the significant benefits of Cur on the protection of fibroblast cells against UVA-induced photo aging and photo carcinogenesis and suggested its potential use in skin photo protection.