In order to treat proliferative IgA Nephropathy(IgAN), The investigators designed an open, prospective, randomized parallel study to access the efficacy and safety of MMF compared to corticosteroid .

Patients who fulfill the inclusion criteria will be randomized in a 1:1 ratio to either the MMF group or corticosteroid group.

To access the efficacy and safety of MMF compared to corticosteroid in in treatment of proliferative IgA Nephropathy(IgAN).

Inclusion Criteria:

1. Patients who signed written informed consent form
2. age between 18-60 years, female or male
3. diagnosed IgA Nephropathy (IgAN) by renal biopsy during 1 months
4. renal biopsy had: 10%< crescents<50%; endocapillary hypercellularity; or necrosis ,and interstitial fibrosis<50%,
5. proteinuria>1g/24h for two times

Exclusion Criteria:

1. secondary IgA Nephropathy (IgAN);
2. eGFR<30ml/min/1.73m2.( MDRD formula)
3. liver disfunction;
4. uncontrolled hypertension
5. WBC <3000/mm3
6. Severe viral infection(HBV, HCV, CMV) within 3 months ofor known HIV infection.
7. diabetes or obesity(BMI>28) ;
8. severe infection or central nervous system symptoms.