The present invention is a blood coagulation reaction inhibitor comprising phosphatidylserine, phosphatidylcholine, and phosphatidylethanolamine. The present invention is also a thrombin generation inhibitor comprising phosphatidylserine, phosphatidylcholine, and phosphatidylethanolamine. The blood coagulation reaction inhibitor and the thrombin generation inhibitor of the present invention are useful as an antithrombotic agent, a clinical laboratory test reagent for the blood coagulation-fibrinolysis system, and the like.
