Abstract: AIM To study the correlation between aldosterone/renin ratio (ARR) and nocturnal blood pressure in patients with essential hypertension. METHODS According to diagnostic and screening criteria, the study included 179 people (88 male and 91 female). The ARR of all subjects, according to the median, were divided into two groups. Monitoring was performed of 24 hour ambulatory blood pressure, serum potassium, serum sodium and other electrolytes. Daytime systolic blood pressure (DSBP), daytime diastolic blood pressure (DDBP), nocturnal systolic pressure (NSBP), nocturnal diastolic pressure (NDBP), medications, serum potassium, serum sodium and other electrolytes were compared between the two groups. RESULTS There were significant differences between the two groups in NSBP, NDBP, blood potassium, sodium (P<0.05, P<0.01), while gender, age, diabetes mellitus, smoking, BMI, DSBP, DDBP, and medicines were not significantly different. After correcting related factors, ARR was positively correlated with DSBP, DDBP, serum sodium (r=0.528, r=0.481, r=0.342, all P<0.05), and negatively correlated with serum potassium (r=-0.354, P<0.05). Multivariate Logistic regression analysis revealed that NSBP and NDBP were independent risk factors for ARR P<0.05), and the 0R values were 1.094 (95%CI:0.906-1.205) and (95%CI:0.919-1.445), respectively. CONCLUSION In patients with essential hypertension, ARR is significantly correlated with nocturnal blood pressure.