Objective To observe the mechanism of anti-renal fibrosis of Kangxianling Decoction（ 抗纤灵方）.Methods Thirty mice were randomly assigned into sham-operated group from 180 C57 mice. The rest 150 mice received 5 /6 renal nephrectomy to establish renal failure model

and then they were equally assigned into model group

low dosage group

middle dosage group

high dosage group and western medicine group. Sham-operated group and model groups were given 0. 5 ml water. Low

middle and high dosage groups were given 0. 5 ml Kangxianling Decoction

0. 2 g / kg

0. 4 g / kg and 0. 8 g / kg

respectively. Western medicine group was given 0. 5 ml sirolimus solution（ 0. 0000016 g / kg）. All the treatments in every group were given by gavage once a day for 12 weeks. On the fourth

eighth and twelfth weekends

10 mice in each group were randomly selected to be executed. Expression of matrixmetalloproteinase 2（ MMP-2） and tissue inhibitor of metalloproteinase 1（ TIMP-1） mRNA in renal tissue were detected. Results Comparing with sham-operated group

levels of MMP-2 mRNA and TIMP-1 mRNA on the fourth

eighth and twelfth weekends in model group were significantly elevated（ P < 0. 01）. Levels of MMP-2 mRNA on the eighth and twelfth weekends in low

middle

high dosage and western medicine groups were significantly lower than those in model group（ P < 0. 05）; while levels of TIMP-1 mRNA on the fourth

eighth and twelfth weekends in low

middle

high dosage and western medicine groups were significantly lower than those in model group（ P <0. 05）. Expressions of MMP-2 mRNA on the eighth and twelfth weekends in high dosage group were significantly lower than those in low dosage group（ P < 0. 05）. In low

middle and high dosage groups

expressions of TIMP-1mRNA were significantly decreased on the eighth and twelfth weekends comparing with those on the fourth weekend（ P < 0. 05）. Conclusion The mechanism of anti-renal fibrosis of Kangxianling Decoction may be associated with inhibition of MMP-2 mRNA and TIMP-1 mRNA expression.