This paper was to explore the effect of blood oxygen saturation (SO2) on oxidative damages of erythrocytes under the condition of oxidative stress. Keeping SO2 of cultured erythrocytes in vitro at the states of 0.3, 0.5, 0.7, 0.9 and 0.98, respectively, we induced oxidative stress by tert-buthylhydroperoxide (BHP, 0.15 mmol/L of final concentration). After incubation, antioxidant capacity was assessed by measuring content of reduced glutathin hormone (GSH) in erythrocytes. Methemoglobin (MetHb) content, lipid peroxidation (thiobarbituric acid-reactive substances, TBARS) and denatured globin-chains on the plasma membrane were measured to assess the extent of oxidative damages. The results showed that in the presence of BHP, GSH contents increased from 0.3 to 0.98 groups; MetHb, TBARS and globin-chains levels all dropped with the rise of SO2. In conclusion, antioxidant capacity and oxidative damages of erythrocytes are closely related to SO2, declined SO2 could promote oxidative damages of erythrocytes.