Abstract: The compressive stress-strain curves of depleted uranium with different grain sizes were obtained over a wide range of strain rates ranging from 10^-3 s^-1 to 10³ s^-1 by static compression test and split Hopkinson pressure bar (SHPB) apparatus, combined with strain frozen technique and optical micrography, the effects of grain size and strain rate on compressive behavior for depleted uranium were discussed. Results show that twinning is the dominant deformation mechanism at the early deformation stage, and the coadjustment and fragmentation of grains are the dominant mechanism when deformation continues. Twinning possess is the major contribution and has lower strength when grain size is larger. Two kinds of depleted uranium with different grain sizes has strong strain rate sensitivity, the number of activated twining systems is smaller when the strain rate is getting higher. Finally, a special form of the Johnson-Cook model was used to describe the mechanical response for depleted uranium.