The influence of extrusion deformation ratio on the dynamic mechanical behavior in a tungsten heavy alloy was investigated under uniaxial compression with loading direction perpendicular to the fiber orientation. With extrusion deformation ratio increasing from 0 to 40.8%, the sensitivity of adiabatic shear banding shows an obviously rising tendency. Microcracks could be seen near the centre of the shear band and initiate at the interface of tungsten-matrix as well as the interior of tungsten. Moreover, the observation by the transmission electron microscopy reveals the dislocation pile-ups at the interface of tungsten-matrix and the presence of a microcrack propagating along the boundary and inside of the subgrain in the interior of tungsten within the shear band