Abstract: This review examines the application value of 24-hour urinary aldosterone in screening for primary aldosteronism (PA). The traditional screening index, the plasma aldosterone-to-renin ratio, is susceptible to multiple interfering factors and suffers from limitations such as high variability and a significant missed diagnosis rate. By integrating 24-hour aldosterone secretion, 24-hour urinary aldosterone can more stably reflect the total aldosterone load and has demonstrated certain practicality in PA screening. The article systematically elaborates on the pathophysiological basis, diagnostic efficacy, differences in cutoff values between domestic and international studies, and the roles of 24-hour urinary aldosterone in subtype differentiation and assessment of target organ damage. It also analyzes the challenges in its clinical application and future research directions, offering a new perspective for early and precise screening of PA.