RACE method was used to obtain the complete cDNA sequence of AmMYB1 (Genbank accession No. KU557504) from ‘Dahong’ amararanth (Amaranthus tricolor L.)，which belong to MYB gene . The AmMYB1 gene contains an open reading frame of 723 bp that encodes 240 amino acids. Comparison between the cDNA and genomic DNA sequences showed that AmMYB1 gene contains one intron. Bioinformatical analysis revealed that AmMYB1 is a typical R2R3MYB containing two consecutive MYB domains.Blast X analysis showed that AmMYB1 is relatively close to betalain biosynthesisrelated BvMYB1，with an identity of 54% .Subcellular localization analysis revealed that the AmMYB1 protein was located in the nucleus. Quantitative real time PCR results showed that the expression level of AmMYB1 was significantly higher in the red part of leaves than that in the green part，and was also higher in the leaves and stems with high betalain concentrations than that in the roots. The expression of AmMYB1 was obviously increased when exposure to light. AmMYB1 was found to be highly expressed in the red leaf variety compared with the green leaf variety. Therefore，the AmMYB1 may play positive roles in regulating betalain biosynthesis in Amaranthus.