Objective: To study on the conformation characteristics of Sophora alopecuroides (SAPS)

its solutions under different conditions and its in vitro anticoagulant activity. Method: The Congo red analysis was used to study the conformation characteristics of SAPS. The changes in SAPS conformations were analyzed by circular dichroism (CD) under different conditions

such as concentration

temperature and adding calcium ions. Finally

the anticoagulant activities of SAPS in vitro was determined. Result: The Congo red analysis showed red shift in the maximum absorption wavelength of SAPS complex. The conformations of SAPS were affected by the changes in the concentration

temperature and metal ions. SAPS with different substitution degrees showed varying degrees of anticoagulant activities. Conclusion: SAPS is a triple helical polysaccharide. Its conformation in solution can be affected by the changes in the concentration

temperature and metal ions. The anticoagulant activities strengthen with the increase in the substitution degree of sulfate radicals.