The corrosion behavior of ultra-fine grain (UFG) copper bulk prepared by equal channel angular pressing (ECAP) was studied in 3.5% NaCl solution. The effect of ECAP deformation on the copper corrosion is controversial in the literature, and worth to verify by means of various experimental techniques. Corrosion performances of UFG copper were investigated in comparison with that in recrystallized coarse grain (CG) copper by polarization curves, Tafel extrapolation method, electrochemical impedance spectroscopy(EIS). The shape of polarization curves and type of corrosive attack remains the same in the UFG and the coarse-grain state. UFG copper exhibited a lower corrosion current and high self-corrosion potential in comparison with CG copper. Electrochemical experimental results showed that UFG copper increased in resistance to corrosion compared with CG copper. This decrease in corrosion resistance was mainly attributed to the more compact corrosion film of UFG copper. The compact passive film led to decrease of the diffusion capability of ions within the corrosion film and corrosion rate.