Inclusion Criteria:  patients aged between 18 to 60 years old scheduled for cardiac valve surgery (replacement or plasty) requiring CPB  Exclusion Criteria:  known allergy to TXA, combined CABG operation or other cardiac procedures other than valve surgery, previous cardiac surgery, EF<45% or cardiothoracic ratio>0.65, serious coagulation disorder, serious hepatic insufficiency, receiving antiplatelet therapy at any time within 7 days of surgery, receiving low molecular weight heparin at any time within 24 hours of surgery, and pregnancy.