The study was included 90 local cows from Al-Rashidea area which locates in the east ofBaghdad city, distributed into three groups, the smallest aged group (30) cows (1.5-2 ) years,middle aged group (30) cows (5.5-7) years and the older aged group (30) cows (11-13) years tostudy the effect progressing of age on some biochemical Criterias as indicators of oxidative stress.The results revealed that the antioxidant enzymes, Glutathione -S-transferase GST was increasedsignificantly (p<0.05) ) in middle -aged group And lower value in the older aging , it was noticedthat arylesterase enzyme gradually decreased significantly with age progress. The non enzymaticantioxidants such as Glutathione GSH revealed with the higher great value in the middle agegroup and the lower significant value in the aging compared with other groups. on the other handMalondialdehyde (MDA) and peroxy nitrite(ONOO-) level gradually increased with progressingof age, these events because of an increasing in production of free radicals and oxidative stressaccompanied with processing of age due to antioxidants depletion, which consider as a defenseline of body against the free radicals effects. It was concluded from this study that with agingprocesses have harm effects on blood components diagnosed by reducing in antioxidants levelsand increasing of Malondialdehyde and peroxy nitrite which consider as an indicators ofoxidative stress and this support the theory of free radicals and oxidative stress and their role inaging processes . Study the effect of aging on some biochemical parameters and antioxidant incow