〔Abstract〕 Objective To study the effect and mechanism of action of Silibinin on the differentiation of 3T3-F442A preadipocytes in murine. Methods The effects of 0-400 μmol/L Silibinin on the proliferation of 3T3-F442A adipocytes at 24, 48 and 72 h were detected by 3-(4,5-dimethylthiazol-2)-2,5-diphenyltetrazolium bromide(MTT) assay, and the effects of Silibinin on the adipogenesis of 3T3-F442A adipocytes were visualized by Oil Red O staining; RT-qPCR, Western blot and ELISA assays were used to detect the effects of Silibinin on 3T3-F442A adipocyte differentiation-associated transcription factor CCAAT/enhancer binding protein(C/EBP) α, C/EBP β, peroxisome proliferator-activated receptor γ(PPARγ), adipocyte protein 2(aP2), adipose generation-associated vascular endothelial growth factor( VEGF)-α and VEGF receptor 2( VEGFR-2),matrix metalloproteinase( MMP)-2and MMP-9,mitogen-activated protein kinase( MEK) and phosphorylated MEK( p-MEK),and extracellular regulated protein kinase( ERK) and phosphorylated ERK( p-ERK) expression. Results MTT assay showed that the cell proliferation rate of 3T3-F442A preadipocytes decreased after 100,200,and 400 μmol/L Silibinin treatment compared with the control group( P<0. 001); Oil Red O staining assay showed that the accumulation of red lipid droplets of the cells in the 160 μmol/L Silibinin assay group significantly decreased; RT-q PCR assay showed that mRNA expression of C/EBPα,C/EBPβ,PPARγ,a P2,VEGF-α,VEGFR-2,MMP-2,and MMP-9 was down-regulated in 3T3-F442A adipocytes treated with 160 μmol/L Silibinin compared with the control group( P<0. 001);Western blot assay showed that protein expression of C/EBPα,C/EBPβ,PPARγ and a P2 was down-regulated in 3T3-F442A adipocytes treated with 160 μmol/L Silibinin( P<0. 001),and the phosphorylation level of p-MEK/MEK and p-ERK/ERK proteins was down-regulated compared with the control group(P<0. 001); ELISA assay showed that the protein concentrations of MMP-2 and MMP-9 in the cell supernatant were down-regulated( P<0. 001) in 3T3-F442A adipocytes treated with 160 μmol/L Silibinin. Conclusion Silibinin inhibited 3T3-F442A adipocyte differentiation and adipogenesis through inhibition of the MEK/ERK pathway and matrix metalloproteinase activity.