【Abstract】 Objective To investigate the clinical effect of reconstruction of old medial collateral ligament by titanium plate autologous peroneus longus tendon. Methods Clinical data of 14 patients with old medial collateral ligament (MCL) injuries of knee in our hospital were retrospectively analyzed, including 8 males and 6 females, aged from 26 to 58 years old (average 42.4 years old). Preoperative and postoperative knee Lysholm score, IKDC score, visual analogue scale (VAS), and medial knee space distance at valgus stress level were statistically compared. Results 14 patients in this group, 1 cases were not followed up, and the rest were followed up for 6-26 months, with an average of (12.57±6.04) months. Lysholm score [preoperative (42.71±6.88) points VS postoperative last follow-up (90.07±2.30) points, T =-22.88, P<0.05]; IKDC score [preoperative (48.71±5.95) VS last postoperative follow-up (83.93±3.79), t=-22.48, P<0.05]; VAS score, [preoperative (8.00±0.96) points VS last postoperative follow-up (0.79±0.80) points, T =18.95, P<0.05]; The medial space of knee valgus at 0° [preoperative (14.48±1.72) mm VS postoperative (4.31±0.33) mm, t=21.23, P<0.05]; The medial space of knee valgus at 30° flexion [preoperative (14.96±1.80) mm VS postoperative (4.50±0.44) mm, t=20.08, P<0.05]. P values of all indexes were < 0.05, showing statistical differences. At the last follow-up, the valgus stress test was weakly positive in 2 patients. Conclusion The reconstruction of the old medial collateral ligament by titanium plate with autologous peroneus longus tendon has a good effect and has the characteristics of small incision, beautiful appearance, quick postoperative recovery and high patient satisfaction.