Background: One of the more significant hormonal systems, the renin-angiotensin-aldosterone system, controls the kidney function, adrenal gland through its effect on the balance of sodium and potassium, blood pressure, fluid volume, and also manages the functions of cardiovascular. Objective: To clarify the interrelationship between renal dysfunction and renin-angiotensin-aldosterone system. Patients and Methods: One hundred samples were collected from December 1, 2022, to February 18, 2023, from Al Shams Medical Laboratories (56 male, and 44) female, age range (of 45-60 years), all of them were volunteers suffering from chronic renal failure in the third stage the average glomerular filtration rate was 35. 70 ± 0.37 125 mL/min/1.73m2. and under conservative treatment. Kidney function test, active renin, angiotensin II, and aldosterone were assessed in the serum of all subjects. The p - value of differences less than 0.05 is measured significant, and uses the statistical package for the social sciences (23) software to calculate the correlation coefficient between various parameters. Results: The result shows relationship between the changes in GFR with creatinine, urea and active renin, the mean GFR showed significant negative correlated with mean creatinine (R = -0.76, p < 0.01. As well as the mean GFR with mean urea (R = -0.64, p < 0.01). The mean GFR also showed significant negative correlated with mean active renin in (R = -0.41, p < 0.01). Also, the mean serum active renin level was significantly positive correlated with mean aldosterone (R =0.33, p < 0.05). Conclusion: Renin enzyme is inversely related to renal dysfunction, so when the glomerular filtration rate decrease, the higher the renin increased, and as a result, the increase in blood pressure in chronic renal failure patients.