Objective：To describe the intra-individual variation of plasma aldosterone concentration(PAC)and aldosterone to renin ratio(ARR)，and to investigate the current situation where positive rate of primary aldosteronism(PA)is based on cut - off values guideline recommended. Methods：Eighty PA patients diagnosed in the Department of Endocrinology，the First Affiliated Hospital of Nanjing Medical University from April 2017 to March 2021 who have 2~4 separated PAC and ARR results on different date were enrolled to calculate the intra-individual coefficient of variation(CV)and percentage difference of PAC and ARR. The percentage of PA patients with single average PAC and ARR below the recommended{PAC＜10，15，20 ng/dL；ARR＜20，25，30(ng/dL)[/ ng/(mL·h)]} were analyzed. Results：Totally 182 plasma rennin activity(PRA)and PAC measurements from 80 subjects were collected. CV of PAC and ARR was 19.74% and 26.11% respectively，the percentage difference was 41.78% and 52.22%. 35.0%，75.0%，93.7% subjects had at least one measurement of PAC lower than 10，15，20 ng/dL respectively；10.0%，37.5% and 72.6% subjects had at least twice PAC lower than 10，15，20 ng/dL respectively. 17.5%，26.3%，36.3% subjects had at least one ARR lower than 20，25，30(ng/dL)[/ ng/(mL·h)] respectively；5.0% ，6.3% ，6.3% subjects had at least twice ARR lower than 20，25，30(ng/dL)[/ ng/(mL · h)]respectively. Conclusion：The PAC and ARR in PA vary greatly in individuals on account of multiple factors. The proportion of single screening values below the positive cut - off values guideline recommended is relatively high，which may lead to false negative rate of PA screening. For suspected patients，screening repeatedly，recalibrating PA screening cut - off point and bringing wider PAC and ARR screening thresholds can improve PA diagnosis rates significantly.