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The diffusion welding (DFW) processing for commercial pure tungsten and CuCrZr alloy was carried out at 900 ~ 980℃ with pressure of 80MPa and holding time of 2h. The high-pressure torsion (HPT) processed for tungsten and CuCrZr alloy with 5 ~ 20 turns were also DFW processed at 900℃, and the W/Cu composite materials with noble interfacial bonding and mechanical property were obtained. The effects of lattice defects induced by HPT on the element diffusion, microstructure evolution and microhardness improvement were analyzed by optical microscopy (OM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The results show that the diffusion depth for W and Cu respectively increase from 0.4μm and 0.9μm to 0.9μm and 1.7μm with the increasing DFW temperature, the high temperature leads to the obvious grain coarsening and microhardness decreasing. The high-density dislocations and ultrafine grains induced by HPT accelerate the element diffusion and immigration during DFW. After 20 turns of HPT followed by DFW, the diffusion depth for W and Cu reach to 2.4μm and 3.1μm, which is the 6 times and 3.4 times higher than the initial. The deformation microstructure of tungsten remained after DFW with slight grain growth to 62μm×25μm and the dislocation density was about 1.5×10₁₄^m_-2^{, which is 36% higher than the initial.} The coarse mixture microstructure of CuCrZr alloy after DFW with HPT composite with annealing twinning grains and equiaxed grains, and the high temperature of DFW lead to complete recovery of dislocations accumulated by HPT. The microhardness of W and CuCrZr after DFW with HPT are about 469 ~ 473Hv_0.5 and 62 ~ 73Hv_0.1 respectively, which is 48% and 9% higher than the value of initial sample with DFW. The results illustrate that HPT processing followed by DFW is benefit to fabricate high performance W/Cu composite materials.