Objective To investigate the effectiveness of the unilateral biportal endoscopy (UBE) technique in the treatment of high-grade migrated lumbar disc herniation (LDH). Methods Between January 2020 and February 2021, 23 cases of high-grade migrated LDH were treated with discectomy via UBE. There were 14 males and 9 females, with a mean age of 48.7 years (range, 32-76 years). All patients had low back and leg pain. The disease duration ranged from 2 months to 7 years (median, 13 months). Lesion segments were L3, 4 in 2 cases, L4, 5 in 15 cases, and L5, S1 in 6 cases. The operation time, intraoperative blood loss, the time when the patients started to move off the floor, and postoperative complications were recorded. The effectiveness was evaluated using the visual analogue scale (VAS) score, the modified Oswestry disability index (ODI), and the modified MacNab criteria. Results All operations were completed successfully, and no complication such as dural tear, epidural hematoma, nerve injury, or vascular injury occurred. The operation time ranged from 53 to 96 minutes, with an average of 71.0 minutes. The intraoperative blood loss ranged from 32 to 56 mL, with an average of 39.3 mL. All patients were removed the drainage tube and wore a lumbar brace to move off the floor around 1 to 2 days after operation. All patients were followed up 3-12 months after operation, with an average of 5.7 months. The VAS scores of low back pain and leg pain and the modified ODI at all postoperative time points were lower than those before operation, and the differences were significant (P<0.05). The differences were significant (P<0.05) when comparing the above indexes between the time points after operation. At last follow-up, the effectiveness was evaluated according to the modified MacNab criteria, and 17 cases were excellent, 4 cases were good, and 2 cases were fair, with an excellent and good rate of 91.3%. There was no recurrence of LDH during follow-up. ConclusionDiscectomy via UBE is an effective method for the treatment of high-grade migrated LDH because of its flexibility, clear view, and wide range of intraoperative exploration, which can effectively reduce the risk of residual nucleus pulposus after operation.