The root system plays vital roles in plant growth, development and yield. In this study, a rice mutant with significantly short roots was isolated from an EMS (ethyl methane sulfonate) generated rice mutant library in the Kasalath background, designated as Osksr5(Oryza sativa kasalath short root 5). Osksr5 showed a dwarf phenotype, the elongation of primary roots, adventitious roots and lateral roots in the mutant was severely impaired, and the number of adventitious roots was reduced. Genetic analysis indicated that the mutant phenotype was controlled by a single recessive nuclear gene. Mapbased cloning analysis located OsKSR5 to a 444 kb region between STS（sequence tagged site）markers 33027k and 33471k on chromosome 1. This result will be helpful for the cloning of OsKSR5 and further characterization of molecular genetic mechanisms underlying root architecture in rice.