Abstract: AIM: To explore the characteristics of vascular function and energy metabolism and mitochondrial function change in aged rats. METHODS: Sixteen rats were divided into two groups (n=8), namely, aged rat group and adult rat group. After 12 h of fasting, glucose and plasma insulin levels were tested. Aortic vascular rings ~2-3 mm were produced and connected to the aortic perfusion and recording system to record the diastolic changes. Blood vessel perfusate was taken to measure NO content. Western blot was used to measure the expression of AMP-activated protein kinase (AMPKα1) using 782-type oxygen consumption apparatus to measure the oxygen consumption of mitochondria. RESULTS: After 12 h of fasting, blood glucose and plasma insulin levels, were higher in aged rat group ［(5.70±0.03) vs.(4.21±0.06)mmol/L, P<0.05］, ［(23.6±0.2) vs.(14.4±0.2)μU/ml, P<0.05］. Diastolic function in aged group decreased significantly ［(0.41±0.01) vs.(0.79±0.01)%, P<0.059). For NO content, there was a significant difference between the aged rat group and adult rat group ［(9.07±0.15) vs.(45.33±0.38) μmol/L, P<0.05］. The expression of AMPKα1 in the aged rat group decreased significantly (P<0.05). For oxygen consumption in mitochondria there was a significant difference between the two groups ［(1.33±0.33) vs.(2.42±0.03) μmol/min/g, P<0.05). CONCLUSION: For the aged rat group, there was a systemic insulin resistance. Vascular diastolic function decreased significantly. AMPKα1 expression and mitochondrial oxygen consumption capacity decreased markedly. It may be one of the mechanisms for decrease of vascular function.