Abstract: Background　Renal injury is a common target organ damage associated with hypertension. Early identification and intervention can help delay or prevent the occurrence of end-stage renal disease. Previous studies have shown that aldosterone levels are independently associated with urinary microalbuminuria in patients with essential hypertension under complete drug washout conditions. However, the impact of aldosterone on renal injury in patients with essential hypertension—including those receiving angiotensin-converting enzyme inhibitors (ACEIs) or angiotensin Ⅱ receptor antagonists (ARBs)—remains unclear. Objective　To explore the effect of aldosterone on kidney damage in treated primary hypertension patients (including those taking ACEI or ARB). Methods　Patients with treated essential hypertension who were hospitalized in the Department of Hypertension, the Sixth Medical Center of PLA General Hospital from January 2021 to October 2024 were enrolled. According to their supine aldosterone levels, participants were stratified into quintiles using the following cutoffs, Q1 group (＜4.8 ng/dL), Q2 group (4.8 - 6.39 ng/dL), Q3 group (6.4 - 8.49 ng/dL), Q4 group (8.5 - 11.24 ng/dL), and Q5 group (≥11.25 ng/dL). Data including sex, age, body mass index, duration of hypertension, blood pressure, heart rate, fasting blood glucose, renal function, lipid profile, renin, aldosterone, 24 h urine protein, and 24 h urinary microalbumin were collected. Multivariate logistic regression analysis was used to evaluate the effect of aldosterone on renal injury in patients with essential hypertension. Results　A total of 895 patients with essential hypertension were enrolled, including 501 males (55.98%), with a mean age of (54.46 ± 14.51) years. The overall plasma aldosterone level was 7.40 (5.30, 10.30) ng/dL. The number of patients in the Q1, Q2, Q3, Q4, and Q5 groups were 177, 184, 173, 182, and 179, respectively. The incidence of renal damage showed an increasing trend with rising aldosterone levels. The number of patients with renal damage in Q1- Q5 groups were 31, 35, 29, 40, and 65, respectively (P＜0.05). Compared with patients in the Q1, Q2, Q3, and Q4 groups, patients in the Q5 group were younger, with higher systolic and diastolic blood pressures, faster heart rates, lower levels of blood potassium and chloride, lower proportion of coronary heart disease, and higher proportion of chronic renal insufficiency. Additionally, 24 h urine protein and 24 h urinary microalbumin levels were higher in the Q5 group. After adjusting for other confounding factors (age, gender, body mass index, systolic pressure, diastolic pressure, smoking history, drinking history, blood potassium, blood uric acid, total cholesterol, triglycerides, ACEI, ARB, calcium channel blockers, diabetes, and coronary heart disease), the risk of kidney damage in the Q5 group was significantly higher than that in the other four groups (OR=2.571, 95% CI: 1.456 - 4.538, P=0.001). In the sensitivity analysis excluding patients receiving ACEI or ARB, the risk of renal damage in the Q5 group remained significantly higher than that in the other four groups (OR=2.387, 95% CI: 1.139 - 5.004, P=0.021). Conclusion　 Elevated plasma aldosterone levels are independently associated with renal damage in patients with essential hypertension. Higher aldosterone levels may contribute to hypertension-mediated renal injury, suggesting the potential value of aldosterone assessment for risk stratification.