This paper has constructed a viscoelastic biomechanical model of the intervertebral disc. In this model, the author takes into account both viscoelasticity of the disc and action of the ligaments,and derives viscoelastic stress and radial bulge formulas when disc is subjected to a constant compression by using linear viscoelastic thoery, and anlyses the distribution of stress and radial bulge in healthy, consolidatory ligaments, degenerated and herniated disc.The computation results coincide with experimental data, and indicate that the maximal initial hoop stress is a major factor that causes dmc injury.