Objective To explore the effect of Rhizoma Polygonati（RP）on arterial aging in naturally aging SD rats. Methods 56 male Wistar rats aged 18 months were randomly divided into 4 groups：an old group，a RP- low，a RP-medium and a RP-high dose group，with 14 rats in each group.Another 14 male Wistar rats aged 2~3 months were selected as the youth group.The RP-high，RP-medium and RP-low dose groups were administered of RP (4，2，1 g/kg) by gavage，the old and youth groups were given the same amount of distilled water once a day for 12 weeks. At week 4 and 12，7 rats from each group were sacrificed?under anesthesia and aortas were isolated.Then the relative contents of smooth muscle cells（SMC）and collagen fiber(CF) were analyzed.The contents of total antioxidant capacity (T-AOC)，glutathione peroxidase (GSH-Px)，superoxide dismutase (SOD) and malondialdehyde (MDA) were measured，and the expression of cell cycle associated proteins in arterial tissue was detected by Western-blot. Results There was no significant change in the indexes of arterial vascular tissue in the old group with increased age.Compared to the youth group at the 4th or 8th week，the aorta in the old group was obviously injured；the relative contents of SMC and CF increased significantly (P<0.01)；the contents of T-AOC，SOD，GSH-Px were significantly decreased，while MDA was increased(P<0.01)。The expressions of cell cycle associated proteins were significantly up-regulated (P<0.01). After RP intervention，the relative contents of SMC and CF were decreased significantly(P<0.05)；the content of T-AOC，SOD，GSH-Px were significantly decreased，while MDA was increased(P<0.05)；The expression of cell cycle associated proteins were significantly decreased (P<0.01). The effect of RP-high dose is better. Conclusion The short-term state of arterial aging in naturally aging rats is stable.RP could delay arterial aging in naturally aging rats by regulating the level of oxidative stress and the expression of cell cycle associated proteins.