Abstract: Based on the investigation of the endosperm structure changes of milled rice under storage, the quality changing mechanism was explored. Microscopic structure of the endosperm cross section, cell surface and starch granules of milled Japonica rice stored under the typical simulation grain storage conditions were analyzed using the Hitachi S3000N scanning electron microscope. The results showed that the radial arrangement tendency of Japonica rice endosperm cross section became blurred, and the starch cell rupture increased, especially in the center region of endosperm cell, with extending of the storage time and increase of temperature. Surface smoothness of endosperm cell decreased, the quantity and size of porosities increased, and the protein membranes of endosperm cell surface had an up wrap appearance and its thickness decreased to some degree. The exposed single starch granules became much more，and the fissure among starch granules rapidly increased, and the protein membranes covered with the surface of some complex starch granules had become blurred and rough. By analysis of the microscopic structure and morphological change of milled rice during storage and the changing mechanism of cooking properties and eating quality of rice, it is demonstrated that the main reason resulted from the rice quality changes during storage is the microscopic structure and morphological changes of rice endosperm, which will offer a theoretical basis for rice storage quality controlling.