Objective To study the occurrence of apoptosis in acute rejection of hamster-to-rat liver transplantation and the molecular mechanism. Methods On the basis of establishment of hamster-to-rat orthotopic liver transplantation, the apoptosis in xenograft were observed by histology and in situ end-lebelling of fragmented DNA;the expression of Fas-L and TGF-?1 were observed by Immunohistochemistry. Rseults In acute rejection of liver xenograft, the apoptosis of hepatocyte was detectable, meanwhile, the expression of Fas-L and TGF-?1 were found. The more severe apoptosis, the more severe acute rejection , and the more expression of Fas-L and TGF-?1 . Conclusions Apoptosis as a mechanism of cell death exists in the acute rejection of liver xenograft, and it is closely related to the expression of TGF-?1 and Fas-L.