Objective: To explore the application value and findings of MR myelogram(MRM) sequence and PROSET sequence in the detection of lumbosacral nerve root anomalies(LSNRA). Materials and Methods: Conventional MRI, 3D MRM and 3D PROSET sequences were performed in lumbosacral nerve roots of 108 cases with low back pain. 3D maximum intensity projection(3D-MIP) reconstruction was used in PROSET and MRM sequences. The lumbosacral nerve roots were observed in the raw images and 3D-MIP images. Results: In the 105 cases with high-quality images, LSNRA were found in the 7, 14 cases with MRM and PROSET sequence. The detection rate was 6.67% and 13.33% respectively. There were statistically significant differences between MRM and PROSET sequence(χ2=5.143, P=0.016). LSNRA were found in only 3 cases with the conventional MRI sequence. Among the 14 cases with variation, there were 10 cases of type Ⅱ(71.43%), which was composed of 4 cases of type Ⅱ-1(28.57%) and each of the type Ⅱ-2, Ⅱ-3 and Ⅱ-4 had 2 cases(14.29% each). There were 2 cases of type Ⅲ, 2 cases of type Ⅵ(14.29% each). Conclusion: PROSET sequence was superior to the MRM sequence in the detection of extradural LSNRA. So it is a good method for the diagnosis of extradural LSNRA.