To investigate the significance of activated platelet levels before and after surgical operation in patients with severed finger by severe injury, the P-selectin (CD62p) positive platelet percent in peripheral blood was studied in 32 patients before and after operation by flow cytometric immunology. At the second and third day after operation, seventeen patients, which in a high positive platelet percent, were measured again after anticoagulation treatment with a large dose of urokinase etc. The results were that the levels of CD62p positive platelet in peripheral blood before and after operation were significantly higher than that of the normal group (P lt; 0.01). The CD62p positive platelet percent was increased not much more in the anti-coagulation patients than in the normal ones (P gt; 0.05). There were a few vascular crisis observed. This study suggested that severed fingers by a crushing or wringing injury enhance the platelet activity and resulted in hypercoagulation, thus anti-coagulation measures should be taken to avoid possible thrombosis and improve the survival rate of replantation. CD62p was one of the sensitive indices of activated platelet, which could be used in calculating hypercoagulation accurately.