Abstract: The existent study was achieved to calculate the toxicity of Calcium Oxide Nanoparticles (CaO-NPs) powder on normal rats following 10 days of oral administration as compared to control. In this study, the adult male albino rats were randomly chosen into (the experimental and control) groups n = 3 which were the orally managed with (50 and 100) mg/kg body weight of (CaO-nanoparticles). The toxic effects were calculated by changes kidney weights and of serum-biochemical considerations such as: Glucose, Blood Urea Nitrogen (BUN), the blood urea, the uric acid and the creatinine. The serum biochemical indicators were experimented in the rats, after 10 days of the post experience. The changes of the serum particular considerations indicated that the kidney were significantly affected in both the experimental groups. The changes among the levels of the total glucose, the blood urea nitrogen, the uric acid and creatinine which that the indicates renal damage in (CaO-nanoparticles) treated male rats. Values shows that the oral administration of (CaO-nanoparticles) may lead to the renal toxicity in the experimental rats. The present study planned to calculate toxic effect of CaO-NPs on biochemical changes in male rats.