[Objective] To compare the clinical outcomes of microendoscopic discectomy system (MED) assisted minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) for spinal canal stenosis accompanied with lumbar instability (LI) versus lumbar spon- dylolisthesis (LS) . [Methods] From May 2005 to May 2018, a total of 935 patients received MED assisted MIS-TLIF for spinal canal steno- sis in our hospital. According to preoperative radiographs, 462 patients were diagnosed of LI accompanied, while the remaining 473 pa- tients had LS. The perioperative, follow-up and imaging documents were compared between the two groups. [Results] All patients in both groups were operated on successfully without serious complications. There were no significant differences between the two groups in terms of operative time, total incision length, intraoperative blood loss, postoperative drainage, walking time, incision healing and hospital stay (P＞ 0.05) . The VAS and ODI scores decreased significantly over time in both groups (P＜0.05) , which in the LI group were significantly better than those in the LS group at 1 and 6 months postoperatively (P＜0.05) , but became not significantly different between the two groups at 12 and 48 months after surgery (P＞0.05) . Radiographically, there was no significant difference in term of Gertzbein-Robbins scales for the ac- curacy of pedicle placement between the two groups (P＞0.05) . Compared with that 6 months postoperatively, BSF fusion classification sig- nificantly upgraded in both groups at 48 months after surgery (P＜0.05) , however, there were no statistically significant differences in BSF classification between the two groups at the any corresponding time points (P＞0.05) . [Conclusion] The MED assisted MIS- TLIF does achieve satisfactory clinical outcomes for spinal stenosis accompanied with both lumbar instability and lumbar spondylolisthesis, and has the advantages of accurate operation under clear vision.