ObjectiveTo compare the effectiveness of unilateral biportal endoscopic decompression and unilateral biportal endoscopic lumbar interbody fusion (ULIF) in the treatment of degreeⅠdegenerative lumbar spondylolisthesis (DLS). MethodsA clinical data of 58 patients with degreeⅠDLS who met the selection criteria between October 2021 and October 2022 was retrospectively analyzed. Among them, 28 cases were treated with unilateral biportal endoscopic decompression (decompression group) and 30 cases with ULIF (ULIF group). There was no significant difference between the two groups (P>0.05) in the gender, age, lesion segment, and preoperative visual analogue scale (VAS) score of low back pain, VAS score of leg pain, Oswestry disability index (ODI), C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), disk height (DH), segmental lordosis (SL), and other baseline data. The operation time, postoperative drainage volume, postoperative ambulation time, VAS score of low back pain, VAS score of leg pain, ODI, laboratory examination indexes (CRP, ESR), and imaging parameters (DH, SL) were compared between the two groups. ResultsCompared with the ULIF group, the decompression group had shorter operation time, less postoperative drainage, and earlier ambulation (P<0.05). All incisions healed by first intention, and no complication such as nerve root injury, epidural hematoma, or infection occurred. All patients were followed up 12 months. Laboratory tests showed that ESR and CRP at 3 days after operation in decompression group were not significantly different from those before operation (P>0.05), while the above indexes in ULIF group significantly increased at 3 days after operation compared to preoperative values (P<0.05). There were significant differences in the changes of ESR and CRP before and after operation between the two groups (P<0.05). Except that the VAS score of low back pain at 3 days after operation was not significantly different from that before operation in decompression group (P>0.05), there were significant differences in VAS score of low back pain and VAS score of leg pain between the two groups at other time points (P<0.05). The VAS score of low back pain in ULIF group was significantly higher than that in decompression group at 3 days after operation (P<0.05), and there was no significant difference in VAS score of low back pain and VAS score of leg pain between the two groups at other time points (P>0.05). The ODI of the two groups significantly improved after operation (P<0.05), but there was no significant difference between 3 days and 6 months after operation (P>0.05). There was no significant difference between the two groups at the two time points after operation (P<0.05). Imaging examination showed that there was no significant difference in DH and SL between pre-operation and 12 months after operation in decompression group (P>0.05). However, the above two indexes in ULIF group were significantly higher than those before operation (P<0.05). There were significant differences in the changes of DH and SL before and after operation between the two groups (P<0.05). ConclusionUnilateral biportal endoscopic decompression can achieve good effectiveness in the treatment of degree Ⅰ DLS. Compared with ULIF, it can shorten operation time, reduce postoperative drainage volume, promote early ambulation, reduce inflammatory reaction, and accelerate postoperative recovery. ULIF has more advantages in restoring intervertebral DH and SL.