Objective To investigate the expressions of transforming growth factor (TGF) -α and -β1 after 90% portal branch ligation (PBL) in rats. Methods Ninety-six SD rats were randomly divided into sham operation group and portal vein branches ligation group. The weight of both ligated and unligated lobes of liver were measured on 0.5, 1, 3, 5, 7, 14, 21, and 28 d after operation. The morphological changes of the unligated liver lobes were observed by microscope. The expressions of proliferating cell nuclear antigen (PCNA), TGF-α, and TGF-β1 of the unligated liver lobes were detected by immunohistochemistry. Results After the ligation of 90% portal vein branches, hepatic lobe at the ligated side diminished progressively after ligation, whereas the lobes of the unligated side underwent compensatory regeneration. The ratio of unligated lobes weight to the whole liver increased slowly within 1 d, speeded up significantly during 1-5 d period, increased slowly on 5 d, and reached plateau phase on 7 d after operation. The expressions of PCNA protein markedly increased within 0.5-3 d (Plt;0.01), which reached the peak on 5 d and decreased slightly on 7 d after operation, but still higher than sham operation group level, and then gradually returned to the level of sham operation group lately. The expressions of TGF-α and TGF-β1 in the unligated liver lobes markedly increased on 0.5 d, and reached the peak on 3 d and 1 d respectively， and then gradually returned to the level of sham operation group in 7-28 d after operation. Conclusion Ligation of 90% portal branches can induce active regeneration of unligated liver lobes in rats, whose initiation and proliferation are involved in the expressions of TGF-α and TGF-β1 protein.