[Objective] To introduce the surgical techniques and preliminary clinical results of simultaneous superficial medial collat- eral ligament (sMCL) and posterior oblique ligament (POL) reconstructions with a half peroneal tendon autograft for old medial collateral lig- ament (MCL) injuries. [Methods] A total of 14 patients had sMCL and POL reconstructed simultaneously with a half peroneal longus ten- don autograft. The anterior half of the peroneal longus tendon was harvested to prepare the graft. After establishing the femoral and tibial bone tunnels respectively, the graft was folded, pulled into the femoral tunnel and fixed with a loop plate. The shorter and longer free ends were pulled into the tibial tunnels of sMCL and POL respectively, and tightened. The two end sutures were tied and enhanced by external row screws. [Results] All the 14 patients were followed up for 6~26 months, with an average of (12.57±6.04) months, except 1 patient. At the latest follow-up, the Lysholm, IKDC and VAS scores were significantly improved compared with those preoperatively (P＜0.05) . Radio- graphically, the inner joint space at 0°and 30° flexion under valgus stress significantly decreased postoperatively compared with those pre- operatively (P＜0.05) . [Conclusion] Simultaneous sMCL and POL reconstructions with a half peroneal tendon autograft does restore the sta- bility of knee joint and considerably improve the function of the knee joint for old MCL injuries, with advantages of small incision, quick postoperative recovery and high patient satisfaction.