Objective To observe the effect of Valsartan on a rat model of acute lung injury and the expression of transforming growth factor-β,TGF-β) ,Smad2/3, Smad7. Methods Twenty-four male adult Sprague-Dawley rats were random divided into three groups : The bleomycin (BLM) group, the control group, and the Valsartan group. Each group contained eight rats. The Valsartan group was treated with Valsartan everyday at a dose of 20 mg/kg after a single intratracheal instillation of bleomycin at a dose of 5mg/kg. BLM group was treated with saline instead of Valsartan after an instillation of bleomycin. The control group was treated with saline instead of Valsartan and bleomycin. Each group was killed at the 7th day after instillation. The lung tissues were harvested for H. E. stain, the immunohistochemistry was used to detect the expressions of TGF-β1, Smad2/3 ,and Smad7. Results The degree of alveolitis in the Valsartan group was ameliorated, compared with those in BLM group (P ＜0. 01). The expressions of TGF-β1 and Smad2/3 in lung tissue of the Valsartan group were significantly lower than that of BLM group(P ＜0. 01). The expressions of Smad7 in lung tissue of the Valsartan group were significantly higher than that of BLM group (0.23 ±0. 02 vs0. 36 ±0.03, P ＜0.01). Conclusions Valsartan could alleviate acute lung injury in rats, which probably be due to the expression decrease of TGF-β1 and Smad2/3 and the expression increase of Smad7 in lung tissues.