Objective To investigate the clinical efficacy of tripterygium wilfordii in the treatment of early diabetic nephropathy and its mechanism .Methods 86 patients with early diabetic nephropathy admitted to Jiaxing Hospital of Zhejiang Provincial Armed Police Corps from December 2015 to December 2017 were selected as research subjects.They were randomly divided into two groups according to the digital table ,with 43 cases in each group .The control group was treated by conventional internal medicine , while the observation group was added tripterygium glycosides on the basis of the control group .The clinical efficacy of the two groups and the changes of serum matrix metalloproteinase-9 (MMP-9) and plasminogen activator -1 (PAI-1) before and after treatment were compared . Results The total effective rate of the observation group was significantly higher than that of the control group (86.04％vs.58.14％)(χ2 =8.323,P=0.004).The MMP-9 and PAI-1 levels and urinary protein of the two groups after treatment were significantly improved ,but the changes of the observation group [ ( 57 .36 ±10 .24 ) ng/L, (24.39 ±7.66)ng/mL,(70.35 ±12.58)μg/min] were more significant than those of the control group [(85.62 ± 15.42)ng/L,(29.64 ±8.61)ng/mL,(102.57 ±20.36)μg/min](t=10.011,P<0.001;t=2.987,P=0.004;t=3.828,P<0.001).Conclusion The therapeutic effect of tripterygium wilfordii in the treatment of early diabetic nephropathy is significant .The mechanism is related to improving the expression of MMP -9 in kidney tissue and reducing the level of PAI-1.