Abstract: The gene of the bHLH transcription factor in purple-fleshed sweet potato was cloned, and its structure, expression pattern and function were studied to reveal its structural characteristics and biological functions. The full cDNA sequences encoding the bHLH gene and having a length of 2 516 bp and 2 304 bp respectively were obtained with the RACE cloning method. The molecular phylogenetic tree analysis based on the DNA sequence showed that the two sequences belonged to the bHLH1 and bHLH2 plant gene families respectively. They were named IbbHLH1 (GenBank accession number: KC708871) and IbbHLH2 (GenBank accession number: JF508437). The IbbHLH1 and IbbHLH2 proteins were localized in the nucleus. The results of semi-quantitative RT-PCR showed that the expression level of IbbHLH2 and that of anthocyanin synthase genes (CHS, CHI, F3H, DFR, ANS and 3GT) were consistent in the roots of three sweet potato cultivars (strains). It is preliminarily speculated that the transcription factor IbbHLH2 is involved in the expression and regulation of a series of enzyme genes in the anthocyanin synthesis pathway of purple-fleshed sweet potato.