Abstract: The bHLH transcription factor family, one of the largest transcription factor families in plants, has been reported to involve in plant growth and salt stress response. In this study, the bHLH transcription factor encoding genes were cloned from barrel clover (Medicago truncatula L.). Bioinformatic analysis showed that the full length of MtbHLH148 cDNA was 1343 bp, Which contained 603bp open reading frame and encoding 201 amino acids. The theoretical pI of MtbHLH148 protein was 11.76 and whoes molecular weight was 22.7 kD. Protein structure analysis showed that the protein had no transmembrane domain, no signal peptide and it was a hydrophilic protein. This gene contained highly conserved bHLH domains. As expected, the secondary structures were predominatly α-helix and random curl, and the proteins were predicted to locate in the nucleus. Phylogenetic analysis revealed that MtbHLH148 was closely related to Glycine max L. Analysis of the cis-regulatory element demonstrated that the promoters of MtbHLH148 contained light, hormone and stress response elements, suggesting their involvement in the biological processes. Analysis of the expression pattern of the MtbHLH148 in barrel clover showed that the highest levle of in stem and the lowest level of in leaf. For treatment, the genes were induced by ABA (100 μmol/L), and were repressed by cold (4℃) but up-regulated by NaCl (200 mmol/L) within the first 8 h. The MtbHLH148 driven by the 35S promoter was separately transformed into Arabidopsis. For Arabidopsis plants over-expressing MtbHLH148, a significantly higher germination rate was observed in spite of their indiscernable phenotypic difference from wild type. Statistical analysis showed that the root length of the transgenic seedlings over-expressing MtbHLH148 was about 1.5 times of the non-transgenic plants, suggesting enhanced salt tolerance. Based on these results, we infer that MtbHLH148 may play a regulatory role in plant response to salinity.