Abstract: Objective: To investigate the therapeutic effect of L-Arginine on ultraviolet-induced skin photoaging in mice and its potential molecular mechanism. Methods: C57BL/6J mice were irradiated with UVB and UVA to successfully establish a skin photoaging model. Meanwhile, the mice were intervened with oral and transdermal administration. Subsequently, the indicators related to skin function and oxidative stress in the serum of each group of mice were measured. Hematoxylin-eosin (HE), Masson, and Toluidine Blue (TB) staining were used to observe the pathological changes in skin structure. Western blot and immunofluorescence were employed to detect the expressions of aquaporin 3 (AQP3) and filaggrin (FLG). Results: After oral or transdermal administration of high-dose L-Arginine, the contents of collagen I (CoL-I), hydroxyproline (HYP), hyaluronic acid (HA), and ceramide (CER) in the serum of mice increased significantly (P<0.05). The activities of total superoxide dismutase (T-SOD) and catalase (CAT) were enhanced (P<0.05), and the level of malondialdehyde (MDA) decreased (P<0.05), which indicated that the antioxidant capacity of mice was obviously improved. Concurrently, the pathological manifestations of photoaging in skin tissue were markedly alleviated, and the expressions of AQP3 and FLG proteins were up-regulated (P<0.05). Conclusion: L-Arginine can effectively alleviate photoaging damage by enhancing antioxidant capacity, promoting skin tissue repair and regulating the expression of key proteins, providing scientific basis and diversified options for the development of functional foods, functional cosmetics and drugs.