Sulfated chitosan and sulfated sodium alginate were synthesized by sulfating reaction of low molecular chitosan and low molecular sodium alginate with SO$_3$-pyridine complex. When the weight ratio of SO$_3$-pyridine complex to polysaccharide was 1:5, the degrees of sulfation were the highest at 2.75 and 2.53 respectively. The anticoagulation effect was the highest when the molecular weight was 8.0${ imes}$10$^3$ Da, and the anticoagulation activity was the highest at 91% of that of heparin when sulfated chitosan and sulfated sodium alginate were mixed at a weight ratio of 1:1. The anticoagulation activity was highest at 84% of that of heparin in the active plastin trombo test (aPTT) when sulfated chitosan and sulfated sodium alginate were mixed at a weight ratio of 1:1.