[Abstract] Objective To observe the effects of hypophysin on coronary blood flow in patients with hypotension after cardiopulmonary bypass (CPB). Methods Twenty-four patients with hypotension after CPB during cardiac valve replacement were intravenously given low dose of hypophsin with the bolus of 0.6 U and the maintaining dose of 1~4 U•h-1. Mean arterial pressure (MAP), heart rate (HR), central venous pressure (CVP), and mean pulmonary artery pressure (MPAP) were monitored continuously and recorded after induction of anesthesia and before CPB (T1), after CPB and before the injection of hypophsin (T2), 5 min after the injection of hypophsin (T3), and at the end of operation (T4), respectively. Diameters of the initiation of left anterior descending coronary arteries were measured through transesophageal echocardiography (TEE) and the minute blood flow were also calculated and recorded at every time points. Results 20 patients completed the study. Compared with T1, MAP decreased （P<0.05）and HR increased （P<0.01）significantly at T2. Compared with T2, MAP increased significantly（P<0.01）, diameters and minute blood flow of the initiation of anterior descending coronary arteries increased significantly at T3（P<0.05 or P<0.01）, MAP still increased （P<0.05）and diameters and minute blood flow of the initiation of anterior descending coronary arteries both increased （P<0.01）at T4. There were no significant changes in CVP and MPAP at every time points. Conclusion Hypophsin can increase the blood flow of coronary artery significantly as well as increase BP in patients with hypotension after CPB.