Microstructure and properties of single crystal copper wire in the condition of strong cold deformation were investigated to understand effects of strong cold deformation on microstructure and properties of single crystal copper wire and its formation mechanism.The results show that similar multi-crystal structure in strong cold deformed single crystal copper wire can be observed

which is attributed to special structure resulting in the generation of sub-grain and micro-phase in later deformation.Electric conductivity is decreased with increasing in deformation rate

where decrement-rate exhibits S line tends

slow-fast-slow.High working hardening rate on OCC single crystal copper rod can be observed during early deformation process

and the working hardening rate is decreased with strong cold deformation process

meanwhile

elongation is slightly decreased

and increment-rate of strength is decreased to a stable value.With elongation less than 3%

single crystal copper wire still realize severe deformation effects.