Objective: To observe the expression of angiotensin converting enzyme (ACE), angiotensin Ⅱ(AngⅡ ), cardiac troponin (cTnⅠ), creatine kinase isozymes (CK-MB) and muscle red protein(Myo) after cardiopulmonary bypass (CPB), and to investigate the association of polymorphisms in angiotensin converting enzyme genes and myocardial injury. Methods: Sixty-three patients suffered from rheumatic mitral stenosis and scheduled for mitral valve replacement with CPB, were randomly divided into three groups according polymorphisms in angiotensin converting enzyme genes: typeⅡ , type ID, type DD (each=21). Blood samples were withdrawn from artery before operation (T1), at the beginning of CPB (T2), 30 min after CPB (T3), (T4) at the end of CPB (T5), 2 h after CPB (T6), 6 h after CPB (T7) to measure the expression of ACE, AngⅡ, cTnⅠ, CK-MB, Myo. Results: The level of ACE during and after CPB were significantly higher than those before CPB (P<0.05). As extension of CPB time, the expression of ACE was increased. The level of cTnⅠ, CK-MB, Myo after CPB were significantly higher than those before CPB(P<0.05). The level of cTnⅠ, CK-MB and Myo were highest at T7, T6 and T5 and T7, respectively. The level of ACE, AngⅡ, cTnⅠin patients with DD genotype was significantly higher than the ID and Ⅱ genotype (P<0.05). Besides, the level of ACE, AngⅡ in patients with ID genotype was significantly higher than the Ⅱ (P< 0.05). Conclusions: There is certain correlation between CPB perioperative midterm ACE and cTnⅠ, Myo, CK-MB. ACE DD genotype is a susceptibility gene of the CPB perioperative myocardial injury.