Objective: Tranexamic acid is an antifibrinolytic agent to reduce blood loss in cardiac surgery. We investigated its effect of different dose in pediatric cyanotic cardiac surgery. Method: Using a prospective, randomized, double-blind study design, we examined 45 patients of cyanotic congenital heart disease of 6 to 22Kg. In group 1 (n=15), patients acted as the control group and receive saline. In group 2 (n=15), the low dose group, patients received tranexamic acid (10 mg/Kg after induction of anesthesia, 10 mg/Kg in the pump prime and 1mg/Kg per 30 minutes during CPB period ). In group 3 (n=15), the high dose group, tranexamic acid was given at the same time point in a fivefold dose. Total blood lose and transfusion requirements during the period from protamine administration until 24 hours after admission to the ICU were recorded. In addition, platelet account and coagulation studies were recorded.Results: The control group had the longest sterna closure time, maximum blood loss at 24 hours, but there is no difference between the two tranexamic acid groups. No significant statistical difference was found in requirements of blood and blood products. In the low dose group, the fibrin account and the platelet account were significantly higher during CPB period and at 4 hours after surgery. No patient in this study required dialysis for renal failure after CPB.Conclusion: Tranexamic acid can reduce perioperative blood loss in pediatric cyanotic heart disease. The low dose group (10 mg/Kg) performed the best effect on the protection of platelet and coagulation parameter.