Objective To evaluate the clinical outcomes of 514 cases of anterior cruciate ligament (ACL) reconstruction using hamstring tendon autograft and to observe postoperative changes and recovery of the grafts through second-look arthroscopy.Methods This retrospective study collected data from 514 patients who underwent ACL reconstruction with hamstring tendon autograft between May 2015 and June 2018, with a follow-up of at least one year. Knee function recovery and stability were assessed using the Lysholm score, International Knee Documentation Committee (IKDC) score, and Tegner score, along with the pivot shift test and Lachman test. During the second-look arthroscopy, key observations included the synovial coverage, continuity of the reconstructed ligament, and any intra-articular abnormalities.Results The time interval between ACL reconstruction and second-look arthroscopy ranged from 12 to 28 months, with an average of 20 months. Postoperative infection occurred in 2 cases, both of which were successfully treated with arthroscopic debridement and drainage. No other patients experienced infections, graft resorption, or other complications. At the second-look arthroscopy, the Lysholm score significantly improved from (43.56 ±9.89) preoperative to (92.21 ± 6.12) postoperatively, the difference was statistically significant (P < 0.05); The IKDC score increased from (20.32 ± 7.87) to (85.67 ± 10.43), the difference was statistically significant (P < 0.05); The Tegner score improved from (4.31 ± 0.82) to (6.61 ± 1.21), the difference was statistically significant (P < 0.05). Second-look arthroscopy revealed that the ligament remained intact in 375 patients, with partial tears in 139 patients, ligament tension was maintained in 447 patients, while 67 patients had laxity, the reconstructed ACL graft was deemed to be in good condition in 435 patients and suboptimal in 79 patients, there were significant differences observed in pre- and post- pivot shift test and Lachman test (P < 0.05); Among the 514 patients, 188 (36.58%) successfully returned to sport.Conclusion ACL reconstruction using hamstring tendon autograft effectively restores knee function and stability. In patients followed for more than one years, the grafts show good vascularization and synovial coverage. Emphasis should be placed on systematic postoperative rehabilitation to optimize recovery.