Abstract: Objective To compare advantages and disadvantages of trans-foraminal (TF) and inter-laminar (IL) percutaneous endoscopic lumbar discectomy (PELD) for the treatment of down migrating L_4-5 lumbar disc herniation. Methods A total of 55 consecutive patients with down-migrated lumbar disc herniation at L_4-5 level who were treated percutaneous transforaminal and interlaminar endoscopic discectomy from June, 2014 to December, 2016 were included in this retrospective study. The patients were divided into two groups according to the treatment they received. Group A was treated by percutaneous interlaminar endoscopic discectomy and group B was treated by percutaneous transformational endoscopic discectomy. The age, sex, degree of herniated disc migration, surgical time, length of hospital stays and related surgical outcomes were all reviewed. Clinical outcomes were measured using pre-operative and post-operative visual analogue scoring (VAS), Oswestry Disability Index (ODI) and Macnab's scoring. The MRI characteristic of different migration degree was also compared. Results The average follow-up time for the 55 patients was 6 month. Compared with group A, group B showed a shorter operative time (P<0.05). The mean VAS and ODI after surgery were improved dramatically in both groups (P<0.05). However, the rate of this change was better in group B as compared group A (P<0.05). There was no significant difference in average rate of change in VAS and ODI score among low-grade down migrating disc herniation group (AL vs. BL), P<0.05. However, among the high grade down migrating disc herniation (AH vs. BH), average rate of change in VAS and ODI score was better in BH than AH group (P<0.05). There were no complications such as dural tear, nerve root injury, infection and hematoma formation in both groups. Conclusion TF and IL PELD are safe and effective surgical approach for down migrating L_4-5 lumbar disc herniation. Compared with TF-PELD, IL-PELD can be more effective treatment for high grade down migrating disc herniation, and it is associated with potential advantages, including surgical time and average rate of change in VAS and ODI score.