Abstract:[Objective] To compare the clinical outcomes of unilateral versus bilateral channel endoscopic decompression in minimally invasive transforaminal interbody fusion (MIS-TLIF) for lumbar spinal stenosis (LSS) . [Methods] A retrospective study was conducted on a total of 90 patients who received MIS-TLIF for LSS in our department from January 2018 to June 2021. According to preoperative doctorpatient communication, 47 patients underwent bilateral decompression through an unilateral channel, with the remained 43 cases received bilateral decompression through bilateral channels. The perioperative conditions, follow-up and imaging data of the two groups were com- pared. [Results] All patients in both groups were operated on successfully with no serious intraoperative complications. The incidence of early complications was of 10.64% in unilateral group, while 11.63% in bilateral group, which was not statistically significant (P=0.881) . The unilateral group proved significantly superior to the bilateral group in terms of operative time, intraoperative blood loss, intraoperative fluoroscopy times and postoperative walking time (P<0.05) , although there was no significant difference in total incision length, incision healing grade and hospital stay between the two groups (P>0.05) . All patients in both groups were followed up for more than 12 months, and there was no statistical significance in the time to resume full weight-bearing activities between the two groups (P>0.05) . The VAS and ODI scores decreased significantly (P<0.05) , while JOA score increased significantly over time in both groups (P<0.05) . There were no sig- nificant differences in VAS, ODI and JOA scores between the two groups before surgery (P>0.05) , however, the unilateral group proved sig- nificantly superior to the bilateral group in abovementioned clinical scores at discharge, 6 months and 12 months after surgery (P<0.05) . Regarding imaging, the height of the intervertebral space, the minimum spinal canal area, and the lumbar lordosis angle significantly im- proved in both groups immediately after surgery and at the last follow-up compared with preoperative results (P<0.05) , whereas no statisti-cal significance was found in the above indexes between the two groups at any corresponding time points (P>0.05) . There was no statistical- ly significant difference in the Bridled fusion grade between two groups at any corresponding time points (P>0.05) . At the last follow-up, all patients in both groups had no adverse imaging manifestations such as screw loosening, fracture, and interbody fusion cage displace- ment. [Conclusion] Both unilateral and bilateral channel decompression in MIS-TLIF do effectively treat LSS. By comparison, unilateral channel decompression achieve better clinical results than bilateral channel, with less intraoperative trauma, earlier postoperative ambula- tion, and faster recovery.