Objective: To investigate the clinicopathological features of idiopathic membranous nephropathy (IMN) and risk factors for decrease of estimated glomerular filtration rate (eGFR), and to provide evidence for the treatment and evaluation of the prognosis in patients with IMN. Methods: The clinical and pathological data of 309 patients diagnosed as IMN from January 2014 to December 2016 were retrospectively analyzed. Results: Of the 309 IMN patients, 288 (93.20%) presented nephrotic syndrome, 21 (6.80%) presented chronic nephritis. A total of 269 patients had eGFR ≥90 mL/(min·1.73 m²), and 40 patients had eGFR <90 mL/(min·1.73 m²). The high-incidence age of IMN is 40–60 years old, males have higher incidence in all ages. A total of 236 (76.6%) patients demonstrated stage II IMN, and the main deposition sites of immune complexes are subepithelial and basement membrane. In the middle and old age groups, the incidence of systolic blood pressure were higher, eGFR and hemoglobin levels were lower, and the degree of renal interstitial lesions was more serious. In patients with eGFR <90 mL/(min·1.73 m²)the blood pressure level and total urinary protein level were higher, serum albumin levels were lower, and renal interstitial pathological changes were more serious. Multivariate analysis showed that high cholesterol, systolic blood pressure, renal interstitial inflammatory cell infiltration, and glomerular sclerosis were independent risk factors associated with decreased eGFR. Conclusion: Control of hypercholesterolemia and hypertension, control of renal interstitial inflammatory cell infiltration and delay of glomerular sclerosis are beneficial to improve the level of eGFR and prognosis in patients with IMN.