Objective: To investigate the efficacy of modified percutaneous Achilles tendon lengthening for severe ankle joint deformity.Methods: This retrospective case series study included 33 patients with an average age of 25.2 years who underwent surgery in our hospital from April 1, 2010 to March 1, 2018. Triple hemisection percutaneous Achilles tendon lengthening was performed. One stage surgery, other soft tissue surgery or bone correction surgery could be performed. After surgery, a plaster cast was used to fix the functional position, and rehabilitation training was carried out as planned. Complications during the perioperative period were recorded. Statistical analysis of the patients' visual analogue scale (VAS) and American Orthopedic Foot and Ankle Society (AOFAS) score before and at the last follow-up was performed. The recurrence rate of Achilles tendon contracture at the last follow-up and the patients' satisfaction rate were investigated.Results: All patients were followed up, with an average follow-up period of 56.31 months (8-104 months). All achieved good ankle joint function and appearance improvement And there were no infection or skin necrosis complications. In two cases, the incision was poorly healed at non-Achilles tendon site and was cured by change of dressing. The average VAS score at the last follow-up was reduced from (2 AE 1.48) points before surgery to (0.26 AE 0.51) points (P = 0.001), and the average AOFAS score was increased from (64.97 AE 13.56) points before surgery to (90.06 AE 10.06) points (P = 0.001). During the follow-up period, there was no chronic rupture of Achilles tendon. There were two cases of recurrence of foot drop (5.7%), and the patients' satisfaction rate was 93.9%. Conclusion:In the surgical treatment of severe ankle joint deformity, the application of triple hemisection percutaneous Achilles tendon lengthening for Achilles tendon contracture has the advantages of less trauma, beautiful incision, and reliable efficacy. The satisfaction rate of patients with this treatment is high, and it is worth promoting in the clinic.