This random, open, control and multicenter clinical trial mainly aims to assess the urine protein remission rate of tacrolimus (TAC) 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 infection, syphilis 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 less than 5 years;
5. Those who received glucocorticoids (prednisone or prednisolone), mycophenolate mofetil, tacrolimus, cyclosporine A, cyclophosphamide, tripterygium and other immunosuppressive agents for treatment within 3 months before screening;
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;