Objective: To investigate the free radical scavenging properties of six aloe species and study its protective effect on red blood cells. Methods: Free radical scavenging properties were investigated in modified chemical system. The antioxidant was purified by silica column and thin layer chromatography and analyzed by HPLC. Its protection on red blood cells was studied with red blood cells culture system in vitro. Results: The extract from A. berebihoria showed the most effective scavenging activities on O - 2? and ?OH (32.19% and 26.05% respectively) in six aloe species. The fraction A with a Rf value of 0 497 was proved to be a pure antioxidant (Rt=15.956 min). It is an anthraquinone with phenol hydroxyls. Fraction A showed strong inhibitory activity on H 2O 2 induced hemolysis of red blood cells and its IC 50 was 0.856 g/L. Conclusion: Fraction A of the extract from A. berebihoria had strong scavenging activities of O - 2? and ?OH, thereby inhibiting the peroxidation of red blood cells and maintaining their functions.