Abstract: Objective TO measure the width of disk-fiavum ligamentum spase(DFLS) and evaluate it's value in diagnose of herniation of intervertibral disk. Materials and Methods The image of CT in lumbar intervertibral disk of 200 cases were retrospectively analyzed; and the shapes of L3-S1 disk, the width of flavum ligmenta at each side and that of DFLS were recorded.. The relation of the restructions and parameters to DFLS stenosis and the compressed lumbar nerve roots shown in CT were analyzed. Results The herniation or bluging of intervertibral disk were found in l96 level; 78 flava ligments width ＞5mm; 172 of 200 cases of mean width DFLS (3.60.8)mm. Conclusion The DFLS£5mm can be diagnosed stenosis. The main causes of stenosis are herniation or bluging of intervertibral disk, flava ligamen thicker. It can be used as a valuable criterion diagnosing lumbar nerve boot compression in CT study.