Abstract: Objective To study the antiacute rejection effect of Pachymic acid (PA) in heart transplantation rats, in order to select a new antirejection medicine with low side effect from traditional Chinese medicine. Methods We established the model by transplanting Wistar rats (32,donor) heart allografts into the abdomen of SD rats (32,receptor). The homologous hearttransplanted rats were then randomly divided into 4 groups with 16 rats in each group. Olive oil solution with PA 1 mg/(kg·d), PA 10 mg/(kg·d), Cyclosporine (CsA) 5 mg/(kg·d) and olive oil solution 0.5 ml/(kg·d) were respectively given intragastrically to lowdosage PA group, highdosage PA group, CsA group and the control group till the end of observation. Survival time of heart allografts, heart beating and the histological changes of allografts were examined and serum level of interleukin2 (IL-2) and interferon-γ (IFN-γ) were determined by enzymelinked immunosorbent assay (ELISA). Results Survival time in the highdosage PA group, the lowdosage PA group and the CsA group were 24.90±0.99 d, 15.50±1.60 d and 26.80±0.88 d respectively, which is much better than the control group (6.10±1.10 d, q=22.363, P=0.000; q=44.793, P=0.000; q=49.272,P=0.000). IL-2 serum level in the highdosage PA group, the lowdosage PA group and the CsA group were all lower than that in the control group (q=14.483, P=0.000; q=3.705, P=0.000; =21.418,P=0.000), whileIL-2 serum level in the highdosage group was lower than that in the lowdosage group (q=10.778,P=0.000). Similarly, IFN-γ serum level in the first three groups were all lower than that in the control group (q=16.508,P=0000; q=4.281, P=0.000;q=19.621, P=0.000) and IFNγ serum level in the highdosage group was also lower than that in the lowdosage group (q=14.975, P=0.000). Pathological examination 7 days after the surgery showed that pathologic lesion was much more relieved in the two PA groups and the CsA group than the control group. Conclusion Acute rejection of heart transplantation can be effectively suppressed by PA.