Abstract: Nanometer rice starch was prepared by super high-pressure homogenization and super-micronization to explore a new method of preparing nanometer starch and to prove its feasibility. Additionally, the particle size, hygroscopic degree, solubility and expansion ratio of nanometer rice starch were studied. The result showed that the super high-pressure homogenization and super-micronization could obviously minish the particle size of rice starch and successfully gain nanometer rice starch. Meanwhile, it indicated that with the reduction in the particle size of the rice starch,its hygroscopic degree,solubility and expansion ratio increased obviously. It showed that the hydration ability of nanometer rice starch was strengthened, which the surface effect and size effect of nanometer rice starch.