AIM: To study the influences of emodin and reconstruction of double blood supplies on liver regeneration of reduced size graft liver in rat model.METHODS: A total of 45 SD-SD rat reduced size liver transplantation models were randomly divided into three groups (A-C). The conventional reduced size liver transplantation was performed on rats in group A, while the hepatic artery blood supply was restored in groups B and C. The emodin (1.5 mg/kg/d) was given by intraperitoneal route in group C only. The recipients were killed on the seventh day after the operation. The proliferative cell nuclear antigen (PCNA), TBil and ALT of serum were detected, and the pathological changes of liver cell were observed. RESULTS: The numbers of the rats that survived in A, B, and C group on the seventh day after operation were 14, 13, 13, respectively. The levels of TBil (31.5±5.2 μmol/L,23.2±3.1 μmol/L vs38.6±6.8 μmol/L), and ALT (5 351±1 050 nKat, 1300±900 nKat vs5779±1202 nKat) in serum in groups B and C were lower than those in group A(P＜0.05), while the expression of PCNA in groups B or C was higher than that in group A (22.0±3.5%, 28.2±4.2%vs18.6±3.2%, P＜0.05). The deeper staining nuclei, double nuclei, multi-nuclei and much glycogen were observed in liver cells of groups B and C, especially in group C, while fewer were found in liver cells of group A. CONCLUSION: The reconstruction of arterial blood supply is very important for rat liver regeneration after reduced size liver transplantation. Emodin has the effect of promoting liver regeneration and improving liver function in rats after reduced size transplantation. The possible mechanism is improving proliferation of liver cell and protecting liver cells from injury.