Abstract: The fine structure of enoxaparin sodium samples with different degree of 1, 6-anhydro derivatives were analyzed with polyacrylamide gel electrophoresis, high performance liquid chromatography, ultraviolet spectroscopy, infrared spectroscopy and nuclear magnetic resonance spectroscopy. A further study of anticoagulation activity of enoxaparins was performed, including those on their inhibition activities of coagulation factor Xa (FXa) and thrombin (FIIa). The results showed that the anti-FXa and -FIIa activities of enoxaparins with different degree of 1, 6-anhydro derivatives (20.0%-39.7%) with similar structure characteristics, had decreasing tendency when the degree of 1, 6-anhydro derivatives increased. Especially, the anti-FXa activity was sensitive to the change of the degree of 1, 6-anhydro derivatives.