Objective Tri ptol ide can suppress immunological rejection reaction. To investigate the effect of tri ptol ide on allogenic tendon transplantation in repairing tendon defect in chicken. Methods The defect model of the third toes tendon was establ ished in 64 healthy-cleaning male Leghorn chickens (4-month-old, weighing 1.9-2.3 kg), which underwent allogenic tendon transplantation for repairing and were divided into 2 groups randomly (n=32). Tri ptol ide feeding[100 μg/(kg·d)] was given for 3 weeks in the experimental group and normal feeding in the control group. General condition of the chickens was observed after operation. The transplanted tendons were harvested from 4 chickens in each group for gross observation at 1, 2, 3, and 4 weeks after operation; the histological observation was performed at 1 and 3 weeks, and transmission electron microscope observation at 2 and 4 weeks. The blood and tendon were harvested from another 8 chickens in each group for flow cytometry and biomechanical tests respectively at 3 and 6 weeks. Results All chickens survived to the experiment end. Gross observation: with time extending, hyperemia and edema around transplanted tendon were rel ieved. Rarefaction adhering zone was seen in experimental group, and pyknotic adhering zone in control group. Histological observation: inflammatory reaction in experimental group was sl ighter than that in control group at 1 and 3 weeks. Transmission electron microscope observation: at 2 and 4 weeks, fibroblasts had big cell nucleus, more euchromatin, and l ittle heterochromatin in experimental group; however, there were small amount of rough endocytoplasmic reticulums with gentle expanded capsular space in control group, which contained sparse content. Flow cytometry test: at 3 and 6 weeks, peri pheral blood contained less CD4+ and CD8+ T lymphocytes in experimental group than in control group, and the ratio of CD4+ to CD8+ T lymphocyte significantly decreased in experimental group when compared with control group (P lt; 0.05). Biomechanical examination: at 3and 6 weeks, the maximum tensile strength in experimental group was bigger than that in control group, and tensile adhesion power in experimental group was smaller than that in control group. There were significant differences in the indexes between 2 groups (P lt; 0.05). Conclusion Tri ptol ide can suppress immunological rejection reaction, strengthen tendon healing strength, and reduce tendon adhesion in allogenic tendon transplantation.