Plant mechanical strength is an important agronomic trait of rice. An ethyl methane sulfonate (EMS)-induced rice mutant, fragile plant 2 (fp2), showed morphological changes and reduced mechanical strength. Genetic analysis indicated that the brittle of fp2 was controlled by a recessive gene. The fp2 gene was mapped on chromosome 10. Anatomical analyses showed that the fp2 mutation caused the reduction of cell length and cell wall thickness, increasing of cell width, and the alteration of cell wall structure as well as the vessel elements. The consequence was a global alteration in plant morphology. Chemical analyses indicated that the contents of cellulose and lignin decreased, and hemicelluloses and silicon increased in fp2. These results were different from the other mutants reported in rice. Thus, fp2 might affect the deposition and patterning of microfibrils, the biosynthesis and deposition of cell wall components, which influences the formation of primary and secondary cell walls, the thickness of cell walls, cell elongation and expansion, plant morphology and plant strength in rice.