Exploring dwarf genes and analyzing their regulatory mechanisms may provide germplasm resources and theoretical bases for maize dwarf breeding. The differences of dwarfing characteristics between maize dwarf mutant K15d and its wild type K15 were analyzed by morphological observation and paraffin section. Based on the result of allelism test， the functional gene in K15d mutant （designated d15） was cloned by PCR amplification， and the expression pattern of d15 gene in stem internodes were analyzed at three stages. Compared with wild type K15， the plant height， ear height and the internodes number below ear position of mutant K15d significantly decreased by 39.22%， 69.75% and 38.83%， respectively. There was no significant difference in cell size in the transverse section of the stem， and the cells in the longitudinal section became shorter and arranged irregularly. The dwarf gene d15 was allelic to br2， showing a 200 bp deletion （5485-5685 bp） at the fifth exon， with the coding region of 3983 bp. The d15-encoded protein had ten transmembrane domains， two less than that of D15-encoded protein， and a second conserved functional domain responsible for substrate binding and transport functions was missing. Compared to the allele br2， only two SNPs differences were observed in the promoter sequence of d15. There were no significant differences in the expression levels of d15 gene between the mutant and the wild type at the three stages of pre-elongation， elongation and post-elongation. In conclusion， the dwarfing characteristics and expression pattern of dwarf gene d15 are similar to br2， which is a new br2 allele and enriches maize dwarf gene resources.