Single lung ischemia-reperfusion injury animal model was used in vivo. Twenty rabbits were randomly divided into two groups (n=10, in each), pulmonary ischemia-reperfusion (IR) group and L-Arg group. The tissue slides were stained by in situ hybridization(ISH) for HO-1 to detect the expression of HO-1 in lung and to analyze the absorbance. Wet to dry ratio of lung tissue weight (W/D) and the injured alveoli rate (IAR) were measured. The lung tissue slide was prepared for electron microscopic observation after 180 min reperfusion. HO-1 expression was upregulated in the pulmonary endothelial cells in two groups. In some pulmonary vascular smooth muscle cells, extima of vessels and epithelial cells of airway, the value of absorbance was 0.148±0.013, 0.158±0.012, respectively, and the activity of HO-1 was 526±65, 784±84, respectively. The L-Arg group showed higher absorbance and activity of HO-1 than the IR group (P<0.05 and P<0.01), lower W/D and IAR values than the IR group (P<0.01) significantly and slighter abnormal changes of the lung tissue in morphologically than the IR group. L-Arg possesses notable protective effects on reperfusion lung in rabbits by increasing the expression and activity of HO-1 in lung tissue.