Objective: To clarify the interaction of the compatibility Erigerontis Breviscapi and Radix Paeoniae Rubra on the thrombus formation and the coagulation time(CT). Method: The arteriovenous bypass thrombogenesis in rats and the CT in mice were as evaluation indicators to evaluate the interaction of the compatibility Erigerontis Breviscapi and Radix Paeoniae Rubra by orthogonal experimental design and variance analysis method

and then pharmacodynamic data were statistically analyzed and estimated whether the two kinds of medicines had interaction. Result: The different combinations of two kinds of medicines could remarkably inhibit the arteriovenous bypass thrombogenesis in rats and significantly prolong CT in mice. The compound compatibility had interaction. Conclusion: The compatibility of Erigeron Breviscapi and Radix Paeoniae Rubra has significant interaction on thrombosis and CT.