Objective:To study the role of iNOS in small-for-size graft. Methods: A non-arterialized partial liver transplantation model was used. Rats were divided into three groups:control group,small-for-size group,Aminoguanidine (AG) group. The expression of the iNOS mRNA and protein,the level of alanine aminotransferase(ALT) in serum,as well as histology were checked after reperfusion. Results: The expression of the iNOS in AG group was lower than that of the small-for-size group,but the expression of ALT in serum sample was significantly higher than that of the small-for-size group(P < 0.05,n = 5). Histology showed necrosis was observed both in the small-for-size group and the AG group. Conclusion: AG can inhibit iNOS in small-for-size graft,but lead to the worse injury.