Abstract: Objective: To investigate the effects of D-galactose induced by different durations on endothelial cell microparticles (EMP) and oxidative stress levels in aging rats. Methods: Forty SD rats were randomly divided into the blank group and the model group. The model group was injected with D-galactose for 6 and 12 weeks, respectively, to establish an aging rat model. HE staining was used to observe morphological changes in the thoracic aorta and liver tissue of the rat. Flow cytometry was employed to measure the levels of EMP in the rat plasma. ELISA was used to detect the levels of SOD and MDA in the liver tissue and the serum IL-6 contents in rats. Results: After 6 weeks of modelling, compared with the blank group, the levels of plasma CD54+ EMP in rats increased, the activity of SOD in the liver tissue was decreased, the content of MDA in the liver tissue and the levels of serum IL-6 increased(P>0.05). However, the difference was not statistically significant. HE staining results indicated that the morphology of the thoracic aorta and liver tissue showed no obvious aging characteristics. However, after 12 weeks of modelling, the level of plasma CD54+ EMP in the model group significantly increased, the activity of SOD in the liver tissue markedly reduced, the content of MDA was substantially elevated, and the level of serum IL-6 was significantly higher than that of the 6-week modelling group(P<0.05). The thoracic aortic intima was noticeably thickened, and the intima/media ratio significantly increased. Meanwhile, the nucleus volume of hepatocytes also markedly increased, the nuclear and cytoplasmic staining deepened, and numerous vacuoles formed, showing obvious signs of aging. Conclusion: Induction with D-galactose for 12 weeks can cause significant senescence changes in rats. Concurrently, the quantity of EMP in plasma and the level of oxidative stress increased with the modelling period. Whereas, modelling for 6 weeks can’t result in significant aging characteristics in rats.