Abstract:[Objective] To explore the effect of different postoperative activities on tendon-bone healing of anterior cruciate ligament (ACL) reconstruction in rabbits. [Methods] Sixty-four 6-month-old New Zealand white rabbits were randomly divided into 4 groups with 16 rabbits in each group, including the immobilized (IM) , free motion (FM) , low-intensity motion (LIM) , and high-intensity motion (HIM) groups. All the animals underwent right knee ACL resection followed by ACL reconstruction with autogenous semitendinosus tendon. The rabbits in the IM group had the knee fixed with plaster cast at 120° flexion after 2 weeks, those in the FM group were placed in free motion without restriction in the cage, whereas those in the LIM group and HIM group ran at 0.2 m/s and 0.5 m/s respectively on the running plat- form, once every 3 days for 0.5 hour each time. At 8 weeks after operation the animals were sacrificed for gross observation, histological ex- amination and biomechanical tests. [Results] Only 3 animals in HIM group showed mild claudication, with positive drawer test, which proved internal fixation failure that the tendon was partially pulled out, but certain length of tendon remained in the tunnel. In term of histo- logical observation, the tendon-bone interface in IM group still had more obvious boundaries and fissures, with more inflammatory cells and vascular tissues, while scanty chondrocytes compared with the FM group. Histological score was ranked from high to low as the LIM group > the HIM group > FM group > IM group with statistically significant differences among them (P<0.05) . In terms of biomechanical tests, the maximum strength to failure was ordered from high to low as LIM group > the HIM group > FM group > IM group with statistically signifi- cant differences among them (P<0.05) , whereas the maximum displacement was arranged from low to high as LIM group < the HIM group < FM group < IM group with statistically significant differences among them (P<0.05) . [Conclusion] In this study, appropriate activities after ACL reconstruction are conducive to tendon-bone healing, whereas complete immobilization or high intensity activities are harmful to ten- don-bone healing.