Background: Lumbar spinal epidural lipomatosis (SEL) is a rare condition characterized by the pathological proliferation of adipose tissue in the epidural space of the spinal canal. This study presents the case of a 59-year- old male with lumbar SEL treated effectively in the short term through arthroscopic-assisted uniportal spinal surgery (AUSS) combined with a modified circle-drawing unilateral laminotomy with bilateral decompression (ULBD) technique. Methods: A modified circle-drawing ULBD procedure was executed via AUSS for a patient with SEL. The procedure involved the excision of diseased adipose tissue from the spinal canal, enlargement and decompression of the spinal canal, liberation of nerves, and post-operative evaluation of imaging results and clinical outcomes. Results: The patient exhibited improvements in the dural sac cross-sectional area, low back pain Visual Analogue Score (VAS, leg pain VAS, lumbar spine Japanese Orthopaedic Association (JOA), and EQ-5D post-surgery. Conclusions: AUSS offers comprehensive visualization, straightforward positioning, facilitating a broad field of view and precise lesion management. The modified circle-drawing ULBD technique characterized by its simplicity, operational freedom, and extensive decompression range, contributes to symptom alleviation and patient recovery.