Background: Idiopathic pulmonary fibrosis (IPF), a chronic, progressive, fibrosing interstitial lung disease, is associated with extremely poor prognosis, and lacks effective treatment. The freguently used immunosuppressive therapies such as dexamethasone (DEX) are often associated with side effects Recently, combination of two Chinese herbal medicine preparations, Salvia miltiorrhiza and ligustrazine (SML), serves as an alternative medicine for treatment of IPF in clinical practices in China. The aim of this study is to compare the anti-fibrotic effect of SML with that of DEX and to investigate the underlying mechanisms.