The study included investigation of effects of the thioredoxin reductase isolated from serum of human on oxidative stress induced in rats, through histopathological examination of the heart and liver, and the measurement of the biochemical parameters, which included: thioredoxin reductase, creatine kinase, alanine aminotransferase, aspartate aminotransferase, total bilirubin, albumin and uric acid. Treating experimental animals with 1% hydrogen peroxide led to a significant increase in thioredoxin reductase, creatine kinase, aspartate aminotransferase and total bilirubin compared to control group, while a significant decrease in: albumin and uric acid, but non-significant in alanine aminotransferase. As well as, a different dose 2 and 4mgl Kg of rat body weight of isolated TrxR with 1% hydrogen peroxide improved parameter levels through decrease oxidative stress that induced in rats. The results of the histopathological examination revealed slight to moderate changes in the heart, while no distinguishing changes were observed in the heart of the group treated with hydrogen peroxide and injected with enzyme in intraperitoneally with 4 mg/ kg of rat weight compared to control group. In the liver, there was observed vascular degeneration and thickening of hepatic capsule as a result of chronic congestion and degeneration in the blood vessels which after treatment with 1% hydrogen peroxide compared to control group, but there was noticeable improvement in the liver of group treated with hydrogen peroxide and injected with the enzyme in intraperitoneally with 4 mg/kg of rat weight, and these results confirm the role of the enzyme in the protection of the body from oxidative stress, the use of the enzyme can reduce the severity of different diseases.