Four specimrens of human carvical spine (C1C7) were selected from fresh cadavers and made into samples for biomedchanical laboratory testiy. The measured critical value of stability loss for normal and healthy cervical spine is 887N, while the ultimate strength 1457N. The magnititudes of these 2 partraeters redueced to 601N and 880N respectively following resection of C5-6. disc. The results indicate that after injury of the disc, the resistance of the cervical spine to external force decreases and futher acute and chronic injury of cervical spine may easily occur.