X-ray diffraction and transmission electron microscopy have been used to study the microstructure of copper foil during rolling. Annealing was used to release work hardening of rolled copper foil (RCF), and electrical conductivity was determined by use of a PPMS-9 comprehensive physical property-measurement system. The microstructure and electrical conductivity of RCF are discussed. Our results showed that the relative intensity of the (220) diffraction peak increased continuously with decreasing sample thickness and that rolling induced preferred orientation. Many obvious crystallographic defects were present; these seriously affected electrical conductivity. The electrical conductivity of RCF decreases with increasing lattice distortion and micro defects which occur during deformation, especially when the surface adsorbs lubricant. However, annealing reduced lattice distortion and the scattering of conducting electrons at these defects, thus improving the electrical properties. For foil thickness in the range 25-180 lm, annealing temperatures in the range 150-300°C, and annealing times in the range 2.5-3.0 h, the electrical conductivity of RCF increased with increasing thickness and annealing temperature, and decreased with increasing annealing time.