To observe the effects of Dahuang Zhechong Pills-containing serum on EMT and the expression of Smad3 and Collagen Ⅲ Protein in A549 cells after TGF-β1 induction based on the hypothesis of “the presence of pulmonary collateral hard blood in IPF patients”，and to explore its role in the prevention and treatment of idiopathic pulmonary fibrosis mechanism.Methods:Normally we grew and took A549 cells in logarithmic growth phase，TGF-β1 intervened for 48 h，observed the morphological changes of A549 cells under electron microscope; choosed pirfenidone as a positive control drug，RT-PCR method to detect the expression of EMT related genes and Smad3 mRNA; Western Blotting was used to detect the expression of Smad3,p-smad3，Collagen Ⅲ protein.Results:The A549 cells with EMT were successfully obtained; the degree of EMT was determined from α-SMA mRNA expression in order from high to low：model group(M)，large-dose group of Dahuang Zhechong Pills containing serum(D)，Western medicine group(P)，middle-dose group of Dahuang Zhechong Pills containing serum(Z)，little-dose group of Dahuang Zhechong Pills containing serum(X)，blank control group(K); Compared with M，the expression of Collagen Ⅲ in Z，X，and P decreased to varying degrees(P<0.05)，and there was no difference in the expression of Z and K(P>0.05); compared with M and K，there was no difference in the expression of Smad3 in each experimental group(P>0.05)，but it had an effect on the expression of its genes and phosphorylation，that is，the expression of Smad3 mRNA and p-smad3.All of them decreased in different degrees(P<0.05).Although the expression in D was lower than M，it was not statistically significant(P>0.05).Conclusion:Dahuang Zhechong Pills has the effect on EMT and the expression of Smad3 mRNA and Collagen Ⅲ in A549 cells after TGF-β1 induction.It is speculated that the protective mechanism of Dahuang Zhechong Pills on IPF may be related to the blocking or reversal of EMT mediated by TGF-β/Smad3 to varying degrees.