To compare the surgical outcomes of autogenous spinous process with iliac bone graft in managing single segment lumbar pyogenic spondylitis (PS) after posterior debridement and instrumentation. We performed a retrospective study for adult patients with single level lumbar PS. 60 patients with single segment lumbar PS underwent one-stage posterior debridement, autogenous bone graft and instrumentations. The patients were divided into Group A (autogenous iliac bone) and Group B (autogenous spinous process). Preoperative Charlson comorbidity index (CCI) was analyzed to assess the comorbidity. Low back pain was evaluated using the visual analog scale (VAS). Neurological status was assessed with the American Spinal Injury Association (ASIA) scale. Clinical infection index including the C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) was also reviewed. Moreover, fusion and changes of sagittal alignment were investigated radiologically. There was a significantly longer operative time, hospital stay and greater blood loss in group A. The VAS scores improved significantly at each follow-up interval and post-operative VAS score was significantly lower in group B. At the last follow-up, ESR and CRP returned to normal for all patients. There was at least one grade level improvement in ASIA score. No statistical difference in corrected rate, loss of sagittal angle and lumbar lordosis was found between the two groups. There was no significant difference in fusion rate, mean fusion time and complications between the two groups. Compared with iliac bone graft, the autogenous spinous process bone graft can be less invasive and painful for the single segment lumbar PS. One-stage posterior debridement, autogenous spinous process bone graft and instrumentation can provide satisfactory results for appropriate cases.