Objective To investigate the effectiveness of slope-reducing tibial osteotomy and anterior cruciate ligament (ACL) revision in the treatment of patients with primary ACL reconstruction failure with abnormally increased posterior tibial slope (PTS). Methods The clinical data of 9 patients with primary ACL reconstruction failure and abnormally increased PTS (≥17°) who met the selection criteria between January 2018 and January 2020 were retrospectively analyzed. There were 8 males and 1 female; the age ranged from 21 to 42 years, with a median age of 30 years. Lachman test was positive in 9 patients; Pivot-shift test was negative in 6 cases, (++) in 1 case, and (+) in 2 cases. The PTS was (17.78±1.09)° and the anterior tibial translation (ATT) was (11.58±1.47) mm. The International Knee Documentation Committee (IKDC) score was 51.0±3.8, Lysholm score was 49.7±4.6, and Tegner score was 3.7±0.7. The time from primary reconstruction to revision was 12-33 months, with an average of 19.6 months. Slope-reducing tibial osteotomy and ACL revision were performed. The improvement of knee subjective function was evaluated by IKDC score, Lysholm score, and Tegner score; Lachman test and Pivot-shift test were used to evaluate the objective stability of knee joint. PTS and ATT were measured before and after operation to observe the morphological changes of knee joint. Results All the incisions healed by first intention, and there was no complication such as incision infection, fat liquefaction, necrosis, deep vein thrombosis of lower extremities, and neurovascular injury. All 9 patients were followed up 12-36 months, with an average of 25.8 months. At last follow-up, Lachman test and Pivot-shift test were negative. IKDC score was 85.0±4.0, Lysholm score was 87.7±2.8, Tegner score was 6.8±0.7, PTS was reduced to (9.89±0.60)°, and ATT was shortened to (0.91±0.29) mm, which were significantly improved when compared with those before operation (P<0.05). Conclusion Slope-reducing tibial osteotomy and ACL revision in the treatment of patients with primary ACL reconstruction failure with abnormally increased PTS has a satisfactory short-term effectiveness. It can improve the stability of knee joint and maintain the normal shape of knee joint.