Abstract: [Objective] To explore the technique and clinical efficacy of Arthroscopic-assisted minimally invasive surgery for chronic tear of the pectoralis major. [Methods] A retrospective study was conducted in 4 patients with chronic tear of the pectoralis major from March 2020 to August 2022. Preoperative ultrasound and MRI were used to accurately evaluate the tear location. The stump end of the pectoralis major muscle was investigated under arthroscopy, and the stump end of the pectoralis major muscle tendon was sutured with the suture hook. Then the scar tissue around the tear was cleaned up with pulling the suture. The insertion of the humerus side of the pectoralis major was explored through the deltopectoral approach. Two holes was drilled in the insertion. The suture was fixed to the lateral margin of the biceps tendon sulcus of the humerus with Footprint anchor. [Results] The operations were successfully completed in all 4 patients without neurovascular injury, infection and other complications. Postoperative MR showed that the pectoral major muscle was normal. The patients were followed up 10-14 months postoperative, with an average follow-up of (11.8±1.5) months. At the last follow-up, the patients had no pain. The active and passive range of motion (ROM) of the shoulder included the abduction, adduction and internal and external rotation has no difference with uninjured side. Pectorals major muscle appeared improved functionally and cosmetically. All patients were returned to sports in 6 months postoperatively. The strength of pectorals major muscle was about Grade 5. All patients were rated excellent by the Bak criteria. [Conclusion] Preoperative magnetic resonance imaging (MRI) and musculoskeletal ultrasound is helpful to display retraction degree and location of pectoralis major muscle tear. Arthroscopic-assisted minimally invasive surgery for chronic tear of the pectoralis major proved to be safe and effective, with good results.