To explore maize dwarf genes and analyze their regulation mechanism, provide germplasm resources and theoretical basis for maize dwarf breeding. Morphological observation and paraffin section were used to study the dwarfing characteristics of maize dwarf mutant K15d and wild type K15. By allele-test, PCR was used to clone the dwarf gene d15, the gene function was analyzed, and the expression pattern of d15 in stem internodes at three stages was analyzed by qPCR. Compared with wild type K15, the plant height, ear height and the internodes number below ear position of mutant K15d decreased by 39.22%, 69.75% and 38.83%, respectively, with significant or extremely significant differences. Stem cells were significantly smaller and irregularly arranged. The dwarf gene d15 was allelic to br2 and consists of 5 exons and 4 introns. The fifth exon was missing 200bp in the range of 5485bp to 5685bp, and the length of coding region was 3983bp which encoded 1326 amino acids. There were only 10 transmembrane domains encoding proteins, two were missing. The change of secondary structure and the loss of the second conserved domain had affected the substrate binding and transport function. The promoter sequence of d15 was 1091bp, and only two SNPs were differences from br2, with 99.94% homology. There was no significant difference between the expression of d15 gene in the mutant and the wild type at the three stages of pre-jointing, jointing and post-jointing. In conclusion, the dwarf gene d15 is a new br2 allele with similar dwarfing characteristics and expression characteristics to br2, which enriches the maize dwarf gene pool.