Abstract: The anticoagulation property of a SWNT membrane is investigated in blood-contacting environments. The adsorption behaviors of fibrinogen, albumin and fresh plasma on SWNT membrane were investigated by scanning electron microscopy (SEM) and energy dispersive X-ray analysis. The platelet adhesion and activation induced by the SWNT membrane were evaluated through SEM observations and fluorescent labeled flow cytometric analysis. Results indicated that the SWNT membrane showed a clear adsorption preference of fibrinogen over albumin. However, there was no appreciable platelet adhesion and activation occurred consequently on a SWNT membrane surface pre-absorbed with fresh plasma, and the percentage of activated platelets caused by a SWNT membrane in a platelet-rich-plasma was about 5%. The conclusion is that the SWNT membrane has unique platelet inertness in blood environments and this anticoagulant effect permits potential use in artificial organs, prostheses and tissue engineering in the cardiac-vascular systems.