This research investigates the link between renal function, hypoxia, and oxidative stress in chronic kidney disease (CKD) through a study involving 76 non-dialysis CKD patients (stages 1-5), 8 healthy subjects, and 24 rats, including 16 CKD models created via 5/6 renal ablation/infarction surgery. The study utilized Blood oxygenation level-dependent magnetic resonance imaging (BOLD-MRI) to measure renal oxygenation and various biochemical indicators to assess renal function and antioxidant capacity. Key findings include significant positive correlations between renal oxygenation metrics (COT2* and MET2*) and estimated glomerular filtration rate (eGFR), as well as between serum superoxide dismutase (SOD) levels and eGFR, COT2*, and MET2*. CKD stages 4-5 patients exhibited notably lower SOD levels. Treatment with losartan in CKD rats improved renal function, fibrosis, and increased COT2*, MET2*, and SOD levels, while decreasing hypoxia-inducible factor-1 alpha (HIF-1α) and malondialdehyde levels. Losartan also positively affected the Keap1-Nrf2/HO-1 pathway, suggesting its potential in alleviating renal hypoxia and oxidative stress in CKD treatment. This study highlights the importance of renal oxygenation and antioxidant capacity in CKD progression and introduces losartan as a promising therapeutic option.