Objective：To quantitatively evaluate nerve roots by measuring fractional anisotropy（FA） values in lumbar intervertebral disc related compression of lumbosacral plexus nerve roots by MR diffusion tensor imaging（DTI）. To evaluate the potential value of DTI in preoperative diagnosis and prognosis evaluation of disc related lumbosacral nerve roots compression. Methods：Thirty-four unilateral disc related lumbosacral nerve roots compression patients underwent MR imaging using diffusion tensor tractography（DTT）. FA values for nerve roots were calculated at three levels from DTI images. Japanese Orthopedic Associationfor the Assessment of Treatment for Low Back Pain（JOA）score and correlation analysis were performed on the clinical function of the patients. Results：The abnormalities of symptomatic nerve tracts were distinctly showed by tractography. On the symptomatic side of nerve roots，the mean FA values displayed a significant declining tendency from proximal to distal. The FA values of the symptomatic side of the nerve roots were significantly lower than those of the asymptomatic side at the proximal，medial and distal levels. The mean FA value of nerve roots correlated moderately with the JOA score. Conclusion：DTI imaging of the lumbosacral plexus nerve roots in lumbosacral nerve roots compression is related to the preoperative evaluation of responsible nerve roots compression of lumbar disc nerve roots. The diversities of nerve roots quantitative FA values reflect the degenerated nerve roots caused by the abnormal sensation and motion dysfunction.