Based on the traditional high-pressure torsion process and the introduction of floating die technology, a high pressure torsion (HPT) process for tungsten and copper alloys with high performance differences was developed. High performance tungsten copper composite materials with good interface bonding were obtained at 300 ℃ and 1.5GPa. The effects of grain refinement and dislocation accumulation on interfacial element diffusion and microhardness during large shear deformation were analyzed by X-ray diffraction (XRD)、optical microscope (OM) and scanning electron microscope (SEM). The results show that with the increase of HPT turns and torsion radius, the equiaxed coarse grains of tungsten are elongated and refined to streamline shape with the average size of 9.0±2 μm after 20 turns and the dislocation density increases to 3.4 × 1014 m-2, which is 2.9 times higher than the initial sample due to the shear deformation. The grain refinement of copper is almost saturated, and equiaxed ultrafine grains with the average size of about 0.3-1.5 μm were obtained within 20 turns of HPT processing. The dislocation density keeps dynamic equilibrium at about 2×1014 m-2 due to the dynamic recrystallization caused by large shear strain. The high-density grain boundaries and dislocations produced by large shear deformation promote the mutual diffusion of tungsten and copper at the interface. With the increase of HPT turns from 10 to 20, the diffusion depth of tungsten and copper increase from 1.2μm and 2.9μm to 1.6 μm and 6.2 μm respectively. Under the effect of grain refinement and dislocation accumulation, the microhardness of tungsten and copper is significantly enhanced to 548.3 ± 360 Hv and 125.0 ± 4 Hv respectively.