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, homologous cloning was used to acquire the MtbHLH148 gene from barrel clover (Medicago truncatula). qRTPCR was used to analyze the expression pattern of MtbHLH148 gene in barrel clover. The overexpression vector was constructed and transformed into Arabidopsis through agrobacterium infection, so as to analyze the related functions of salt tolerance of transgenic Arabidopsis. The result shows: (1) the full length of MtbHLH148 cDNA was 1 343 bp, Which contained 603 bp 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 structure was predominatly αhelix and random curl. (2) Subcellular localization results showed that the proteins were locate in the nucleus. (3) Phylogenetic analysis revealed that MtbHLH148 was closely related to Glycine max 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. (4) qRTPCR analysis of the expression pattern of the MtbHLH148 in barrel clover showed that the highest level in stem and the lowest level 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. (5) The pCAMBIA3301MtbHLH148 overexpression vector was successfully constructed and transformed into Arabidopsis. We obtained 16 resistant lines and identified 12 overexpressed lines. Among these overexpressed lines, the transgenic line OE8 had the highest expression level. Analysis of salttolerance function of OE8 showed that a significantly higher germination rate was observed in spite of their indiscernible 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.