Basic helix-loop-helix protein (bHLH) is an important transcription factor in eukaryotes, and it is mainly composed of basic amino acid region and helix-loop-helix region. In this study, a total of 122 mung bean bHLH transcription factors were identified by bioinformatical methods, and their physicochemical properties, conserved domain, gene structure, chromosome distribution, family evolution and expression differences of some typical bHLH genes were analyzed. The results show their physicochemical properties were different. The bHLH contained two conserved domains, which were located in the alkaline amino acid region of N and the helical ring and spiral region of C, respectively. There were five conserved motifs, and the basic amino acid region contained the conserved sequence: His5-Glu9-Arg13, and they were related to the binding with the target gene, while HLH region contained two conserved residues, Arg23 and Arg55, which were related to the formation of dimer. The bHLH genes were uneven distribution on the 11 chromosomes in mung bean. The number of genes on chromosome 5, 7 and 8 were larger, and the number of genes on chromosome 1, 4 and 10 were smaller. The number of introns ranging from 1 to 9, and the genes were clustered on some chromosomes. The phylogenetic analysis showed that 122 bHLH transcription factors were divided into 11 subgroups. Our results showed that the expression of bHLH is diverse and exhibit distinct patterns in different tissues of mung bean. This study lays a foundation for further study on the complex biological functions of bHLH transcription factor family in mung bean.