Abstract: [Objective] To observe the safety and superiority of clinical research on the treatment of lumbar nerve root canal stenosis by posterior-approach endoscopy through the internal opening of intervertebral foramen using small bone drill, large circular saw and tunnelling. [Methods] A total of 80 hospitalized patients with lumbar nerve root canal stenosis from January 2017 to May 2019 were selected and randomly divided into the treatment group (small bone drill, large circular saw and tunnelling) with 40 patients and the control group (percutaneous endoscopy through the interbody approach) with 40 patients using a randomization list. VAS and JOA were scored before operation, and at 1 day, 1 week, 1 month and 6 months after operation respectively, and the treatment outcome was evaluated. [Results] There was no statistically significant difference in VAS and JOA scores between the treatment group and the control group before operation, while the difference between the treatment group and the control group at 1 day, 1 week, 1 month and 6 months after operation compared with that before operation had a significance level of P<0.01. The average time to establish the tunnel was significantly superior in the control group than in the treatment group. However, the average time of endoscopic decompression, total operation time and average length of hospital stay were significantly superior in the treatment group than in the control group. No serious surgical complications occurred in either group. [Conclusion] The clinical research techniques for treatment of lumbar nerve root canal stenosis by posterior-approach endoscopy through the internal opening of intervertebral foramen using small bone drill, large circular saw and tunnelling are easy to master. The combination of small bone drill and large circular saw can avoid the compression on nerve roots and reduce the risk of using circular saw. The handling of bony tissue is simple and rapid, and the tunnel has high range of motion. The removal of intervertebral discs on the lateral side of nerve roots has advantages such as less interference to nerve tissue, sufficient decompression of nerve tissue, and excellent treatment outcome.