Objectives To determine compressive force on anterior and posterior wall of the dura under posterior compression by ligamentum flavum with incremental compression ratios and different compression shapes in all posture. Methods Round bone window was drilled between C4 and C5 vertebral body of five fresh C2-C7 cervical spines. A compression-inducing pole (CIP) was made and slided into the bone window to simulate the hernia of ligamentum falvum. The compression ratio ranged from 10% to 60% of the canal diameter, a force record pole (FRP) and an anterior window were also made to record the compressive force caused by posterior compression. Results When the compression ratio is low (10%-20%), the compressive force is the biggest in left bending (30°). When the compression ratio is high (50%-60%), the compressive force is the biggest in flexion (30°). The compressive force on anterior wall of the dura is around 27.8% of that on posterior wall in all compression ratios, which enlarged with increase of the diameter of the CIP. Conclusion The force induced on the dura relate strongly with the compression ratio, the diameter of CIP and the posture of the cervical spine. Compressed spinal cords are easy to be deteriorated in full flexion and full extension.