Objectives: The purpose of this study was to investigate the antithrombotic effect of Carthamus tinctorius. Methods: SD rats were used to investigate the inhibitive effect of platelet aggregation (in vitro & in vivo), prothrombin time, platelet count. Mice were used to investigate the survival rate after injection of collagen & epinepbrine. Results: 1. The inhibitive effect of platelet aggregation (in vitro & in vivo) were increased significantly in all groups. 2. Prothrombin time was decreased in both groups. 3. Platelet count was decreased significantly in sample A. 4. Survival rate after injection of collagen & epinepbrine was increased in sample B. Conclusion: According to the above results, it is suggested that Carthamus tinctorius has antithrombotic effects.