A dwarf and fragile mutant temporarily designated as dwf1 was screened out in the progeny of an excellent indica restorer line Jinhui 10 with seeds treated by ethyl methane sulfonate(EMS). As compared with the wild type, its plant height was shorter with drooping leaves, the roots, stems, leaves and grains of dwf1 displayed extremely brittle during its whole growth period. Agronomic traits such as plant height, panicle length, seed setting rate, internode length and 1000-grain weight was lower at different degrees than those of the wild type. Comparing of the mechanical strength between dwf1 and Jinhui 10 showed that dwf1’s mechanical strength obviously decreased. Moreover, cellulose and lignin content in dwf1’s cell wall decreased, hemicellulose content increased, and silicate content had no significant difference. Genetic analysis demonstrated that the mutational characters were controlled by a single recessive nuclear gene. A single base missense mutation arised on the seventh extron in DWF1 (LOC_Os09g25490) in dwf1 when compared with the wild type, resulting in an amino acid change from cysteine to arginine. Homologous comparison revealed that this mutation occurred in DWF1’S highly conserved region. These results of dwf1 contribute to mutational mechanism research of rice dwarf and brittle mutants.