Objective To investigate the impact of sarcopenia on effectiveness of lumbar decompression surgery in patients with lumbar spinal stenosis. Methods The clinical data of 50 patients with lumbar spinal stenosis who met the selection criteria between August 2017 and December 2020 were retrospectively analyzed. According to the diagnostic criteria of the European Working Group on Sarcopenia in Older People (EWGSOP), based on the calculation of the skeletal muscle index (SMI) at the L3 level, SMI<45.4 cm2/m2 (men) and SMI<34.4 cm2/m2 (women) were used as the diagnostic threshold, the patients were divided into sarcopenia group (25 cases) and non-sarcopenia group (25 cases). There was no significant difference in gender, age, disease duration, level of lumbar spinal stenosis, surgical fusion level, and comorbidity between the two groups (P>0.05); the body mass index in sarcopenia group was significantly lower than that in non-sarcopenia group (t=−3.198, P=0.002). Clinical data of the two groups were recorded and compared, including operation time, intraoperative blood loss, postoperative drainage volume, hospitalization stay, and complications. The visual analogue scale (VAS) scores of low back pain and sciatica and Oswestry disability index (ODI) scores were recorded preoperatively and at last follow-up. The effectiveness was evaluated according to modified MacNab standard. Results There was no significant difference between the two groups in terms of operation time, intraoperative blood loss, and postoperative drainage volume (P>0.05). However, the hospitalization stay in sarcopenia group was significantly longer than that in non-sarcopenia group (t=2.105, P=0.044). The patients were followed up 7-36 months (mean, 29.7 months). In sarcopenia group, 1 case of dural tear and cerebrospinal fluid leakage occurred during operation, as well as 1 case of internal fixator loosening during follow-up; 1 case of incision exudation and poor healing occurred in each of the two groups, and no adjacent segment degeneration and deep vein thrombosis of lower extremity occurred in the two groups during follow-up. There was no significant difference in the incidence of complications (12% vs. 4%) between the two groups (χ2=1.333, P=0.513). VAS scores in low back pain and sciatica as well as ODI scores in two groups significantly improved when compared with preoperative results at last follow-up (P<0.05). The differences of VAS scores in low back pain and ODI scores before and after operation in sarcopenia group were significantly lower than that in non-sarcopenia group (P<0.05). However, there was no significant difference of that in VAS scores of sciatica between the two groups (t=−1.494, P=0.144). According to the modified MacNab standard, the excellent and good rate of the sarcopenia group was 92%, and that of the non-sarcopenia group was 96%, showing no significant difference between the two groups (χ2=1.201, P=0.753). ConclusionPatients with sarcopenia and lumbar spinal stenosis may have longer postoperative recovery time, and the effectiveness is worse than that of non-sarcopenic patients. Therefore, for elderly patients with lumbar spine disease, it is suggested to improve preoperative assessment of sarcopenia, which can help to identify patients with sarcopenia at risk of poor surgical prognosis in advance, so as to provide rehabilitation guidance and nutritional intervention in the perioperative period.