Tacrolimus Monotherapy for Idiopathic Membranous Nephropathy (IMN)

Inclusion Criteria: 1. Age: 18 - 80 years; 2. Those whose clinical manifestation and renal biopsy pathologic diagnosis are IMN (Stages I-IV) with secondary membranous nephropathy excluded; 3. Those who meet any of the following high-risk IMN standards: * Urinary protein\>8g/24h * Serum albumin\<25g/l * Serum PLA2R levels are 5 times higher than normal * eGFR decline rate after confirmed IMN within 6-12 months is ≥30% * Patients with serious complications: pulmonary embolism, lower extremity static Vein thrombosis/embolism, acute renal injury, etc. 4. Those without reaching the above high-risk IMN standard, but their course of disease is \>6 months without spontaneous remission,and still present nephrotic syndrome; 5. Patients who have signed the informed consent forms. Exclusion Criteria: 1. Those whose kidney pathological manifestation of interstitial fibrosis is \>30%; 2. Those who are positive in active Hepatitis B (including HBsAg, HBeAg and HBcAb or HBsAg, HBeAb and HBC) or serological indexes (HBsAg or/and HBeAg or/and HBcAb) or infected with Hepatitis C, tuberculosis, cytomegalovirus, severe fungal or HIV infection; 3. Those who suffer from untreated active digestive tract ulcer within 3 months before random grouping; 4. Those who suffer from uncured malignant tumor for less than 5 years 5. Those who received glucocorticoid (prednisone or prednisolone), mycophenolatemofetil, tacrolimus, cyclosporine A and other drugs for treatment within 3 months before screen with a course of treatment exceeding 4 weeks or those who received cyclophosphamide (accumulated dose\>1.0g); 6. Those whose ALT, AST or total bilirubin content goes beyond 1.5 times above normal upper limit; 7. Those who suffer from combined critical complications such as serious infection or other severe organ disease or dysfunction; 8. Pregnant or lactating women; 9. Those who are known to be allergic to drugs under trial or relevant products; 10. Those who participated in other clinical trials within 3 months before inclusion; 11. The patients who cannot comply with the research proposal as determined by the supervising physician. Exit criteria 1. Those with incomplete or partial relieved proteinuria for 6 months after treatment; 2. Patients or their legal guardians voluntarily requests to withdraw; 3. Those against the inclusion criteria and exclusion criteria; 4. Those who need to take medications prohibited by the trail; 5. Those with poor compliance or stopping the drug for over 2 weeks; 6. Those with uncontrollable infection; 7. Those whit elevated blood glucose during the treatment, which is still difficult to control after routine treatment by endocrinologists; 8. In the TAC group, the eGFR decreased by \>30%, the TAC dose was halved. And the drug concentration and renal function were reviewed after 2 weeks. If the eGFR decreased by \<30%, it will continue to be used; if the eGFR still decreased by \>30%, the TAC dose continues to halve, or give a minimum dose of 0.5mg / d. And the drug concentration and renal function were reviewed after 2 weeks. If the eGFR decreased by \<30%, TAC will continue to be used, otherwise stop the drug; 9. Those whose ALT, AST or bilirubin rises to more than 2 times the upper limit of normal value after treatment, and continues to increase for 2 weeks; those whose ALT, AST or bilirubin rises to more than 2 times the upper limit of normal value after 2 weeks of treatment with liver protection, the drug will be discontinued. If it cannot be recovered after 2 weeks, the patient will withdraw; 10. Those with other unexplained severe comorbidities; 11. Those with pregnancy during treatment; 12. For security reasons, the research sponsor proposed to stop the study;