copper,an essential trace element for animals,is also essential for mitochondrialfunction,it is a prosthetic cofaetor for Cu/Zn-SOD,COX and monoamine oxidase(MAO),whichare common exist in mitochondria. In this study,experiment was performed to examine the effectof dietary copper supplementation on mitoehondrial function of liver in broiler chicken. Onehundred and sixty 1-day-old cobb 500 broilers(Gallus domesticus,BW =43±0.32 g) werestratified by weight and randomly assigned to four dietary treatments of 40 broilers each,whichcontained 11(control),110,220 and 330 mg of supplemental Cu/kg DM as CuSO4. All of theexperimental broilers were fed with corn-soybean meal containing supplemental copper for 60days； Liver mitoehondrial function of broiler chicken was recorded on days old of 12,24,36,48and 60. copper supplementation had no significant influence on mitochondrial function(RCR andP/O) and mitoehondrial complex(Ⅰ,Ⅱ,Ⅲ,Ⅳ,Ⅴ) in the treatment group supplemented with 11 mgCu/kg DM(P > 0.05). The supplement providing 110 mg Cu/kg DM increased mitochondrialfunction and the activities of complex Ⅰ-Ⅴ and had significant difference after 36 day-oldcompared with other groups(P<0.05). RCR,P/O and complex Ⅰ-Ⅴ experienced an enhanced trendin the treatment group supplemented with 220 mg Cu/kg DM and 330 mg Cu/kg DM on days oldof 12,24 and 36,but subjected decrease(P<0.05) on 48 and 60 day-old except complex IV(P >0.05). Cu accumulation in liver and mitochondrial H2O2 production were increased(P < 0.05) byall Cu supplemented treatments during the feeding trail with the increase of dietary level of Cu inthe diet of birds,especially in the treatment group supplemented with 220 mg Cu/kg DM and 330mg Cu/kg DM. In conclusion,supplementation of the basal diet with 110 mg Cu/kg DM enhancedmitochondrial function and the activities of mitochondrial complex,but high dietary copper(with220 mg Cu/kg DM and 330 mg Cu/kg DM) appears to undermine the liver mitochondrial functionand complex activities except for complex Ⅳ which had more resistant to high liver copperaccumulation. There were increases in liver copper accumulation and mitochondrial H2O2production with the increase of dietary level of Cu in the diet of birds,the results of these studiesprovide insight into understanding subcellular mechanisms associated with the dietary copperoxicity in birds.