Objective To compare the effectiveness of posterior lumbar interbody fusion (PLIF) by unilateral fenestration and bilateral decompression with ultrasounic osteotome and traditional tool total laminectomy decompression PLIF in the treatment of degenerative lumbar spinal stenosis. Methods The clinical data of 48 patients with single-stage degenerative lumbar spinal stenosis between January 2017 and June 2017 were retrospectively analyzed. Among them, 27 patients were treated with unilateral fenestration and bilateral decompression PLIF with ultrasonic osteotome (group A), and 21 patients were treated with total laminectomy and decompression PLIF with traditional tools (group B). There was no significant difference in gender, age, stenosis segment, degree of spinal canal stenosis, and disease duration between the two groups (P>0.05), which was comparable. The time of laminectomy decompression, intraoperative blood loss, postoperative drainage volume, and the occurrence of operation-related complications were recorded and compared between the two groups. Bridwell bone graft fusion standard was applied to evaluate bone graft fusion at last follow-up. Visual analogue scale (VAS) score was used to evaluate the patients’ lumbar and back pain at 3 days, 3 months, and 6 months after operation. Oswestry disability index (ODI) score was used to evaluate the patients’ lumbar and back function improvement before operation and at 6 months after operation. Results The time of laminectomy decompression in group A was significantly longer than that in group B, and the intraoperative blood loss and postoperative drainage volume were significantly less than those in group B (P<0.05). There was no nerve root injury, dural tear, cerebrospinal fluid leakage, and hematoma formation during and after operation in the two groups. All patients were followed up after operation, the follow-up time in group A was 6-18 months (mean, 10.5 months) and in group B was 6-20 months (mean, 9.3 months). There was no complication such as internal fixation fracture, loosening and nail pulling occurred during the follow-up period of the two groups. There was no significant difference in VAS scores between the two groups at 3 days after operation (t=1.448, P=0.154); the VAS score of group A was significantly lower than that of group B at 3 and 6 months after operation (P<0.05). The ODI scores of the two groups were significantly improved at 6 months after operation (P<0.05), and there was no significant difference in ODI scores between the two groups before operation and at 6 months after operation (P>0.05). At last follow-up, according to Bridwell criteria, there was no significant difference in bone graft fusion between the two groups (Z=–0.065, P=0.949); the fusion rates of groups A and B were 96.3% (26/27) and 95.2% (20/21) respectively, with no significant difference (χ2=0.001, P=0.979 ). Conclusion The treatment of lumbar spinal stenosis with unilateral fenestration and bilateral decompression PLIF with ultrasonic osteotome can achieve similar effectiveness as traditional tool total laminectomy and decompression PLIF, reduce intraoperative blood loss and postoperative drainage, and reduce lumbar back pain during short-term follow-up. It is a safe and effective operation method.