Fine grain 93W-4.9Ni-2.1Fe-0.03Y% alloy was strengthened by rapid hot extrusion. The dynamic mechanical properties and failure behavior were investigated for the rapid hot extruded fine grain tungsten heavy alloy at high strain rates. The results show that the flow stresses of the as-extruded fine-grained tungsten alloy at relatively lower strain rates are equivalent, of the order of 2000 MPa. Tungsten particles on the fracture surfaces are severely deformed and fracture into fine pieces which adhere to the soften matrix phase. This phenomenon is enhanced with the strain rate increasing. Observation of the sectioned surfaces reveals that the tungsten particles are heavily shear deformed along the fracture surface, but no plastic deformation is observed when it gets into the interior, indicating the localized shearing marks. The experimental results have proved that the failure of the extruded fine-grained tungsten heavy alloy is adiabatic shearing failure.