Abstract: The structure and blood anticoagulating activity of two sodium cellulose sulfates, i.e. Na-MCS and Na-CAS were studied.Na-MCS and Na-CAS were derived from microcrystalline cellulose(MC) and cellulose tri acetate(CTA) respectively by sulfation with ClSO3H-DMF.Structural measurement by IR spectra disclosed the presence of sulfate bond in both Na-MCS and Na CAS.Elemental analysis revealed that the substitution degree of Na-MCS and Na-CAS were 1.70 and 0.83 respectively.Further measurement of 13CNMR showed that the distribution of sulfate was complete substitution at C_6, partial substitution at C_2 in Na MCS and only patial substitution at C_6 in Na-CAS.Anti-coagulation investigation indicated that the re calcium time(RT) of whole blood, and the activated partial thromboplastin time(APTT) and throbin time(TT) of human plasma were prolonged when Na-MCS or Na-CAS was added. Compared with sodium heparin, the blood anticoagulating activity of Na-MCS was even stronger, while the anticoagulation activity of Na-CAS was much weaker than that of Na-MCS.