Besides internal and external stress, the injury to rice grains is concerned with mechanical properties. In this paper, the force-deformation curve of rice grains was measured by the compression test. Some phenomena that occurred in the compression test were described. Compression failure force and compression failure energy are two important indexes to the mechanical properties of rice grains. The influence of different varieties, harvest time and after ripening action on mechanical properties of rice grain was determined respectively. The differences of mechanical properties between rice grains (with husk) and brown rice (without husk) were put forward. The significant effect of husk on reducing the injury to rice grains was shown. The mechanical parameters of rice grains can offer the base for optimization design of relevant devices.