Anticoagulant activities were tested for the fifteen kinds of medicinal plants by measuring activated partial thromboplastin time (aPTT). Of them five kinds or species (Artemisia princeps, Sanguisorba officinalis, Artemisia apiacea, Eclipa alba, Schizonepeta tenuifolia) were selected and fractionated for the preparation of acidic polysaccharides. They were extracted with water by refluxing and the extracts were precipitated with ethanol. The precipitates were separated based on charge using a DEAE-Sephadex. The low salt and high salt fractions were sulfated with anhydrous pyridine and chlorosulfonic acid complex. In vitro anticoagulant activities of sulfated polysaccharides were tested by measuring aPTT, prothrombin time (PT), and factor Xa clotting time using normal human plasma. No relationship was found between the amount of uronic acids and anticoagulant activities, but the sulfated ones show the increase of activities. In vivo anticoagulant properties of the sulfated polysaccharide from Artemisia apiacea were also tested by the intraveneous administration of three different doses (3,5 and 10 mg/kg) to rats. APTT and PT were increased significantly and the action of factor Xa and thrombin mediated through antithrombin III were inhibited slightly.