Abstract: Basic/helix-loop-helix(bHLH) is an important transcription factor commonly existed in eukaryotes, it participates in the regulation of many physiological pathways. In order to clarify its function and regulation mechanism in tobacco, a bHLH gene, NtbHLH93, was cloned from Nicotiana tabacum by homologous cloning technology, and its biological function was predicted by bioinformatics combining with gene expression pattern analysis. The results showed that the cDNA sequence of NtbHLH93 was 1254 bp in length with an open reading frame(ORF) of 1047 bp and encoding 349 amino acids. NtbHLH93 was a hydrophobic protein, the main elements in its secondary structure were α-helix and random coil, and its tertiary structure featured helix-loop-helix structure typical of bHLH family. The gene expression of NtbHLH93 was obviously tissue-specific, highly expressed in lateral roots at different growing stages and in the ovary at flowering stage, which was consistent with the feature that the synthesis of plantsterol concentrated in meristematic tissues.