Objective　To discuss the safety range of spinal canal decompression via intervertebral disc approach.　Methods　Cervical vertebra specimens from 18 embalmed adult cadavers were dissected for observing anatomic features of the dura mater, posterior longitudinal ligament and anterior epidural space. The thickness of dura mater, the width of posterior longitudinal ligament and the sagittal diameter of vertebral body at the intervertebral disc level were measured and analyzed.　Results　The posterior longitudinal ligament composed of deep and superficial layers, which separated from each other leaving the median line about 4 to 5 mm.  The anterior epidural space was composed of the superficial layer of posterior longitudinal ligament and dural mater. We also identified Hofmann ligament anterior to the dura mater, attaching the dura to the posterior longitudinal ligament. Deep and superficial layers formed a fusiform space, which was named as the posterior longitudinal ligament space. The distance from the middle of posterior margin of intervertebral disc to the lateral angle of each side of the space was about 10 mm.　Conclusions　The cervical anterior approach could reach the posterior longitudinal ligament through intervertebral disc, and enter the posterior longitudinal ligament space. This approach is valuable for protecting dura mater, spinal cord and spinal roots.