Abstract: Sheep blood as the research material, the ovine thrombin was extracted from it by adsorption method.The main factors that influence the specific activity of ovine thrombin were researched by single factor and orthogonal tests.The results showed that the influencing sequence from significant to common was pH, activation temperature, concentrations of Ca2 +and activation time, and the final optimal parameters were pH 5.2, activation time was 2.5h, activation temperature was 30℃ and concentrations of Ca2 +was 0.1mol /L.Under these conditions, the specific activity of anticoagulant blood plasma was 268.3U /mg.