Objective To compare the effect of dexmedetomidine and nitroglycerin for controlled hypotension and the changes in cerebral oxygen metabolism during intracranial aneurysm surgery. Methods 60 patients with intracranial aneurysm surgery were randomly divided into 2 groups(n=30 each group): dexmedetomidine group (group D) and nitroglycerin group (group N). Group D: Continuous infusion of dexmedetomidine was start at 1 μg/kg 10 min later, adjust infusion rate to 0.4 μg•kg-1•h-1-0.8 μg•kg-1•h-1 according the changes of mean arterial pressure（MAP）. Group N: continuous infusion of nitroglycerin was start at 3 μg•kg-1•min-1.10 min later, adjust infusion rate to 3 μg•kg-1•h-1~9 μg•kg-1•min-1 according the changes of MAP. MAP and heart rate (HR) were recorded at before induction,at controlled hypotension,10, 20 min and 30 min after controlled hypotension and 30 min end of controlled hypotension（T,T0,T1,T2,T3,T4）. Simultaneous acquisition radial artery and jugular venous bulb blood line blood gas analysis, calculation of cerebral oxygen uptake rate (CERO2). Results MAP in the two groups reached the target blood pressure within 30 min of controlled hypotension started. During controlled hypotension, HR and CERO2 in group D: T3[(66 ± 10) bpm, (27 ± 6) % was lower than T0(76 ± 9) bpm, (35 ± 6) %] (P <0.05). HR in group N : T3 (86 ± 8) bpm was higher than T0 (77 ± 8) bpm (P <0.05).There were no significant of CERO2 between T3 (32 ± 6)% and T0 (34 ± 5)% in group N (P> 0.05). CERO2 and MAP was positively correlated in group D(r= 0.83). Conclusions Dexmedetomidine for controlled hypotension in intracranial aneurysm surgery is safe and reliable. Compared with nitroglycerin, dexmedetomidine can reduce HR and cerebral oxygen metabolism.