Objective To assess the effectiveness of arthroscopic capsular release to treat primary severe frozen shoulder through trans cuff portal. Methods Between June 2012 and January 2015, 28 patients with primary severe frozen shoulder were enrolled in the study. There were 8 males and 20 females with an average age of 57 years (range, 42-81 years). The left shoulder was involved in 16 cases and the right one in 12 cases. The mean disease duration was 11 months (range, 7-21 months). Six patients had diabetes. All patients underwent arthroscopic capsular release by trans cuff portal. The range of motion (ROM) of the shoulder were measured at preoperation and at 6 weeks and 24 months after operation; the scores of American Shoulder and Elbow Surgeons (ASES) and visual analogue scale (VAS) were used to evaluate the shoulder function and pain. Results Primary healing of incision was obtained, and no complications of infection, shoulder instability, and nerve injury were found. All patients were followed up 24 months. Pain of the shoulder was obviously relieved; VAS score was significantly lower at 6 weeks and 24 months after operation than preoperation (P<0.05), and at 24 months than 6 weeks (P<0.05). ROM of the shoulder and ASES score at 6 weeks and 24 months after operation were significantly increased when compared with preoperative ones (P<0.05); significant difference was found in ROM of forward flexion and external rotation and the ASES score between at 6 weeks and 24 months (P<0.05). And internal rotation in-creased from trochanter (9 cases), hip (6 cases), sacrum (7 cases), and L4 vertebral level (6 cases) before operation to the T12-T6 vertebral level at 6 weeks and 24 months after operation, which were close to normal side. Conclusion Arthroscopic capsular release through trans cuff portal is an effective and safe management for primary severe frozen shoulder.