Objective To explore the clinically significant cut-off value of serum anti-PLA2R antibody (sPLA2R-Ab) in adult idiopathic membranous nephropathy (IMN) in Baoding City. Methods A total of 285 patients who underwent renal needle biopsy and sPLA2R-Ab detection in Baoding First Central Hospital from January 2018 to December 2021 were included. The patients were divided into IMN group, secondary membranous nephropathy (SMN) group and other groups. The level of sPLA2R-Ab was compared between the groups; the correlation between sPLA2R-Ab level and other clinical indicators in IMN patients was analyzed; logistic regression was applied to identify the risk factors of IMN; the diagnostic value of sPLA2R-Ab for IMN was analyzed by ROC curve, and Youden index was calculated to obtain the optimal cut-off value of sPLA2R-Ab for IMN diagnosis. Results The level of sPLA2R-Ab in IMN group was significantly higher than that in SMN group and other groups(P<0.05). In IMN group, sPLA2R-Ab was negatively correlated with total protein and albumin(P<0.001), it was positively correlated with 24h urinary protein, serum creatinine and cholesterol(P<0.05). ROC curve showed that the cut-off value of sPLA2R-Ab in the diagnosis of IMN patients was 3.315RU/mL, the corresponding Youden index was the highest (0.651), the sensitivity was 79.4%, the specificity was 85.7%, the AUC was 0.829, P<0.001. Conclusion sPLA2R-Ab is associated with the activity of IMN disease. The cut-off value of SPLA2R-AB for differentiating IMN from non-IMN patients is 3.315RU/mL, which can improve the early diagnosis rate of IMN.