The rapid development of new energy vehicles has generated considerable interest in the efficient production of ultrafine aluminum electronic wiring harnesses with superior strength and electrical conductivity (EC). However, achieving a balance between strength and EC/ductility remains a challenge. To overcome the trade-off relation, we precisely controlled the grain size and grain boundary structure by using ultrafine aluminum powders (∼1 μm) as the starting material, and introduced dislocations into the as-sintered sample to enhance the strain rate sensitivity via cold deformation. In the cold-deformed sample, a unique mechanical response was observed: the elongation increased with deformation. Meanwhile, the strength and EC maintained to be a high level. Based on the unique properties, we successfully fabricated kilometer-scale ultrafine aluminum wire (0.2 mm in diameter) by cold deformation without any intermediate annealing, realizing high strength (206 MPa) and high EC (59.1%IACS, International Annealed Copper Standard) simultaneously. Our work provides a new concept and a new processing route to efficiently produce ultrafine aluminum electronic wiring harness with excellent properties.