Abstract:[Objective] To introduce the surgical technique and preliminary clinical consequences of arthroscopic assisted small-inci-sion repair of pectoralis major tear. [Methods] From March 2020 to August 2022, 4 patients underwent abovementioned operation for oldpectoralis major tear near the humeral insertion. After preoperative ultrasonography and MRI were used to show the exact location of the in-jury, the torn pectoralis major was identified under arthroscopy, and then the free end of the pectoralis major tendon was sutured with inter-locking suture by suture hook. The tendon end was released under traction with the suture loop and removing the scar tissue around the inju-ry site under arthroscope. A small incision was made on the deltopectoral groove to expose the anatomic insertion of pectoralis major, holeswere drilled at the humerus, and the tendon was reduced to the lateral margin of the biceps tendon groove of the humerus, and fixed with afootprint anchor. [Results] All the 4 patients were successfully operated on without neurovascular injury, infection and other complications,and were followed up for 10~14 months with an average of (11.8±1.5) months. At the last follow-up, all patients had no pain, regained nor-mal range of motion in terms of abduction-adduction and internal-external rotation, with significantly improved function and appearance ofthe pectorals major, and resumed sports 6 months after surgery with grade 5 pectoral muscle strength. Based on Bak's criteria, all 4 patientsachieved excellent results. The postoperative MR showed that the pectoral major muscle was in normal appearance. [Conclusion] Preopera-tive MRI and musculoskeletal ultrasonography can help to reveal the retraction and quality of the torn pectoralis major. Arthroscopic assist-ed small-incision repair of old pectoralis major muscle tear is feasible and minimally invasive, and does achieve satisfactory preliminaryclinical results.