Objective we observed the level of TGF-β1 in serum and urine，and investigated the relationship between MMF and immunoglobulin A nephropathy(IgAN),to explore the possible mechanisms of MMF to IgAN. Methods the sample was divided into three groups: health control group（Group C）that was composed of 19 healthy volunteers, Group IgAN that was formed by 39 patients without any treatment, and MMF treatment group included 48 patients treated with MMF. The level of TGF-β1 in serum and urine was detected in all sample of three groups by ELISA, the result of which was compared among three groups. Results Comparing with Group IgAN, lower level of TGF-β1 in the serum were found both in Group C and Group MMF（38242.4±18217.9vs29092.5 ±6583.7，23237.2±15107.3 pg/ml， P=0.036，P=0.00047）. Comparing with Group IgAN, lower level of TGF-β1 in urine were found in Group C and Group MMF（77.12 ±48.13vs45.59 ±4.78 ,58.52±32.53 pg/mg Cr，P=0.00000009，P=0.00017）. The level of TGF-β1 in Serum was positively correlated with pathological grading and urinary protein excretion (p=0.044, 0.001).  The level of TGF-β1 in urine was negatively correlated with  glomerular filtration rate(GFR)（p=0.012）and positively correlated pathological grading, serum creatinine, and urinary protein excretion(p=0.01, 0.013, 0.000039)in IgAN patient. Comparing with the Lee grade ≤ 3 ,patients  with > Lee grade 3  had higher level of TGF-β1 both in serum (P=0.049)and urine(P=0.028). The patients were grouped according to the Oxford classification score and  found that the patients with T ≥ 1 had higher level of TGF-β1 in urine than T = 0(P=0.043). In Group MMF, comparing with the patients who had been treated with MMF less than 6 months, the patients with treatment of MMF more than 6 months exhibited significantly decreased level of TGF-β1 both in serum (P=0.001）and urine(P=0.026). Conclusion the level of TGF-β1 in serum and urine was significantly elevated in IgAN patients, and its expression is significantly  related to the progress ， severity of renal function and the damage of tubulointerstitial. MMF could make the level of TGF-β1 in serum and urine in IgAN significantly reduced, especially in the patient had the treatment more than 6 months. Therefore, the level of TGF-β1 in serum and urine can be considered as an important indicator not only to predict the progression of IgAN, but also to assess the therapeutic effect of MMF in IgAN.