he dynamic mechanical properties of fine-grained tungsten heavy alloy 93W-4.9Ni-2.1Fe with trace yttria addition were investigated under dynamic compression using Split Hopkinson Pressure Bar. The microstructure of the alloy sample after dynamic compression was analyzed. The results reveal that two obvious adiabatic shear bands were observed at the strain rate of 1900 s-1, indicating that the susceptibility of the fine-grained alloy to local adiabatic shear is significantly enhanced and the fine-grained alloy can form the shear bands at a lower strain rate. The adiabatic shear bands initiate in the crack tip region of the surface area of the specimen, propagating deeply along orientations at 45o to the impact direction. The bands have much narrower width of about 10-25 mm than that of traditional tungsten heavy alloy. Within the center of the bands, the tungsten grains are severely elongated to be fibrous along the propagation directions of the adiabatic shear bands, exhibiting plastic flow localized instability