Erect leaves are one of the important indexes for improving plant architecture and breeding dense-planting cultivars. In this study, an erect leaf (designated el, tentatively) mutant was identified by ethyl methyl sulfonate (EMS) induced mutagenesis in sorghum BTX623. The leaves of the mutant were erect from the six-leaf stage to the whole growth stage. At heading stage, the leaf length and width of the first leaf to the seventh leaf in mutant was significantly decreased. The leaf angle was larger at the lower leaves but became smaller at the upper leaves; the lamina joint length (except that the last leaf pillow is not formed) and auricle perimeter of each node showed the opposite trend. At the maturity stage, significant difference on spike length, grain number per panicle and growth period were observed while no significant difference on plant height, grain length, grain width, seed setting rate and 1000-grain weight was detected. Genetic analysis revealed a 3:1 separation ratio of the wild and mutant phenotype in F2 isolated population, implying that erect leaf was controlled by single recessive gene. Paraffin section analysis showed that this phenotype was caused by the increased number of lobar ear cells and lobar small vascular bundles. The results gained from this experiment laid a foundation for future gene cloning, and also provided gene resources and theoretical support for the analysis of the mechanism of sorghum leaf erect change and the breeding of dense planting cultivars.