Objective The anterior cruciate l igament (ACL) is the important stable structure of the knee. To evaluate the method and outcome of bone-ACL-bone (B-ACL-B) allograft under arthroscope in reconstruction of ACL. Methods Between October 2007 and February 2010, arthroscopic ACL reconstruction with deep-freezing B-ACL-B allograft was performed on 22 patients with ACL ruptures. There were 15 males and 7 females with an average age of 27.6 years (range, 19-55 years). The causes of ACL rupture were sport trauma in 12 cases, fall ing injury in 1 case, heavy crush in 2 cases, and traffic accident in 7 cases. The locations were the left knee in 14 cases and the right knee in 8 cases. The disease durationwas 7 days to 12 months (median, 65 days). Nineteen patients showed the positive results of anterior drawer test and pivot shift test, and 21 patients showed the positive results of Lachman test. According to International Knee Documentation Committee (IKDC) criteria, there were 5 abnormal and 17 severely abnormal. The subjective IKDC score was 49.6 ± 6.9. The Lysholm score was 48.5 ± 5.3. The Tegner scale scores were 6.8 ± 1.2 before injury and 2.1 ± 0.5 before operation. The MRI showed the ACL injuries in 18 of 20 patients. Results The mean operative time was 75 minutes (range, 65-85 minutes); the mean blood loss was 110 mL (range, 80-150 mL). All incisions healed by first intention. No immunologic rejection and deep vein thrombosis of lower l imbs occurred. All patients were followed up 7-34 months (mean, 18 months). At last follow-up, the flexion of the knee ranged from 125 to 135° (mean, 130.5°). Two patients showed the positive results of anterior drawer test, 1 patient showed the positive result of pivot shift test, and 3 patients showed the positive results of Lachman test. According to the IKDC criteria, 10 patients rated as normal, 11 patients as nearly normal, 1 patient as abnormal. The subjective IKDC score was 90.0 ± 5.8, showing significant difference when compared with preoperative one (t=4.653, P=0.021). The Lysholm score was 91.6 ± 7.1, showing significant difference when compared with preoperative one (t=4.231, P=0.028). The Tegner scale score was 6.1 ± 1.5, showing no significant difference when compared with one before injury (t=1.321, P=0.070) and showing significant difference when compared preoperative one (t=3.815, P=0.033). The arthroscopic examination showed no rupture of grafts in 19 patients, 17 grafts showed normal tension, and 2 showed sl ight relaxation at 6 months after operation. Conclusion Reconstruction of the ACL with B-ACL-B allograft under arthroscope is a safe and effective method, which can anatomically reconstruct ACL and obtain a good recovery of the knee function after operation.