OBJECTIVE： To evaluate the effects of dexmedetomidine priming solution on the hemodynamics of heart surgery patients during cardiopulmonary bypass （CPB）. METHODS： 80 patients with rheumatic heart disease （RHD） undergoing selective aortic and mitral valve replacement were divided into control group （group C） and dexmedetomidine group （group D）， with 40 cases in each group. The dexmedetomidine 1 μg/kg was added to the priming solution of the extracorporeal circulation in group D， and an equivalent volume prime without dexmedetomidine was received in group C. MAP and HR of 2 groups were observed at pre-parallel stage of CPB. The amount of vasopressor drugs （metaradrine） and antihypertensive drugs （phentolamine） during CPB， the change of MAP and medication interval before and after the use of antihypertensive drugs were observed in 2 groups. The amount of narcotic drugs were recorded in 2 groups during CPB. The levels of serum IL-6 and TNF-α in 2 groups were determined 5 min before anesthesia induction （t1）， 5 min before CPB （t2）， 30 （t3）， 60 min （t4） during CPB， after CPB （t5）， 2 （t6）， 12（t7）， 24 h （t8） after surgery. The time and case number of cardiac resuscitation， the occurrence of arrhythmia were observed in 2 groups. Pre- and post-parallel cycle time and aortic cross-clamp time were observed in 2 groups. The amount of dopamine were observed in 2 groups at different stages after cardiac resuscitation. The occurrence of bradycardia was observed in 2 groups after cardiac resuscitation. RESULTS： Compared to group C， the MAP was increased in group D at pre-parallel stage of CPB， while HR and the amount of metaradrine and phentolamine were decreased significantly； medication interval was prolonged significantly， and the amount of midazolam and propofol were decreased significantly， with statistical significance （P＜0.05）. Serum levels of IL-6 and TNF-α in 2 groups were increased gradually as time after CPB， and reached the maximal value at the end of CPB （t5）. Compared with t1， serum levels of IL-6 at t3-t8 and serum levels of TNF-α at t2-t8 were increased significantly in 2 groups. Compared with group C， serum levels of IL-6 at t4-t7 and serum levels of TNF-α at t3-t7 were decreased significantly in 2 groups， with statistical significance （P＜0.05）. There was no statistical significance in the time and case number of cardiac resuscitation， case number of ventricular fibrillation after resuscitation， pre- and post-parallel cycle time and aortic cross-clamp time between 2 groups （P＞0.05）. The amount of dopamine in 2 groups decreased gradually as time after resuscitation， but there was no statistical significance among different stages between 2 groups （P＞0.05）. No bradycardia was found in 2 groups after resuscitation. CONCLUSIONS： Dexmedetomidine 1 μg/kg in the priming solution could prevent transient hypotension of heart surgery patients at the beginning of CPB， and relieve the hypertension during CPB.