Objective To investigate the effects of D-galactose induction for different durations on endothelial cell microparticles (EMP) and oxidative stress levels in aging rats. Methods Forty Sprague-Dawley rats were randomly divided into four groups: blank group 1, blank group 2, model group 1 and model group 2. Rats in the model group were injected with D-galactose for 6 and 12 weeks, respectively, to establish an aging rat model.Morphological changes in the thoracic aorta and liver tissues were detected by hematoxylin / eosin ( HE) staining. Plasma levels of EMP were measured by flow cytometry. Liver levels of superoxide dismutase ( SOD) and malondialdehyde (MDA) and serum interleukin ( IL)-6 were measured by enzyme-linked immunosorbent assay. Results After 6 weeks of modelling, plasma levels of CD54⁺EMP were increased significantly (P<0. 05); SOD liver activity was decreased(P>0. 05), and liver MDA and serum IL-6 levels were showed only an upward trend compared with the blank group 1(P>0. 05); however, the differences were not significant (P>0. 05). HE staining indicated no obvious aging characteristics in the thoracic aorta and liver tissue. After 12 weeks of modelling, however,plasma CD54⁺EMP levels increased significantly (P<0. 01), SOD liver activity decreased (P<0. 01), MDA levels were substantially elevated (P<0. 01), and serum IL-6 levels were significantly higher compared with the 6-week modelling group ( P<0. 01). The thoracic aortic intima was noticeably thickened and the intima / media ratio was significantly increased ( P<0. 05). The hepatocyte nuclear volume was also markedly increased, nuclear and cytoplasmic staining deepened, and numerous vacuoles formed, showing obvious signs of aging. Conclusions Induction with D-galactose for 12 weeks can cause significant senescence changes in rats. Concurrently, EMP plasma levels and oxidative stress levels increased with increasing modelling period. In contrast, modelling for 6 weeks result ed in no significant aging characteristics in rats.