A dwarf mutant of rice (Oryza sativa L.) by mutagenesis of ethylene methylsulfonate (EMS) treatment from Nipponbare was identified. The mutant exhibited phenotypes of dwarfism and withered leaf tip (dwl1). Based on the internode length of dwl1, this mutant belongs to the dm type of dwarfing. Analysis of elongation of the second sheath and alpha-amylase activity in endosperm showed that the phenotype caused by dwl1 was insensitive to gibberellin acid treatment. Using a large F2 population derived from a cross between the dwl1 and an indica rice variety, TN1, the DWL1 gene was mapped to the terminal region of the long arm of chromosome 3. Fine-mapping delimited it into a 46 kb physical distance between two STS markers, HL921 and HL944, where 6 open reading frames were predicted. Cloning of DWL1 will contribute to dissecting molecular mechanism that regulates plant height in rice, which will be beneficial to molecular assisted selection of this important trait.