High pure tungsten (W, 99.99%) were prepared by chemical vapor deposition (CVD), then high pure tungsten and polycrystalline tungsten prepared by powder metallurgy (PM) process were impacted using Split Hopkinson Bar (SHB) over a narrow range of strain rates, 1000 s-1~2000 s-1. The deformation mechanisms were analyzed by optical microscope (OM). The results show that the main deformation mechanisms of the polycrystalline tungsten prepared by Powder Metallurgy Process are slip and grain-boundary slide, while those of high pure tungsten are slip, twinning deformation and grain-boundary slide. The interaction between the neighbouring twinnings may induce two kinds of intergranular cracks, which is the key reason of the high pure tungsten em-brittleness. The adiabatic shear band (ASB) is not found for the high pure tungsten under the strain rate in this paper e.g. lower than 103 s-1, so the plastic deformation ability of the high pure tungsten can not be improved as that of tungsten heavy alloy (WHA).