Study was designed to explore the effect of sodium tanshionone IIA sulfonate on bleomycin-induced pulmonary fibrosis in rat. The amount of lipid peroxides (LPO), hydroxyproline in rat lung tissue homogenate was determined at 3, 7, 14, 28 day after administration respectively. The results suggest that the amount of LPO, hydroxyproline of rat lung homogenate were significantly decreased in sodium tanshionone IIA sulfonate group. In addition, histological changes and width of alveolar septa and percentage area of pulmonary fibrosis scars was measured. The results show that sodium tanshionone IIA sulfonate could ameliorate bleomycin induced pulmonary fibrosis in rat. The mechanism that sodium tanshionone IIA sulfonate could prevent and treat bleomycin-induced pulmonary fibrosis in rat was discussed.