Effects of ultraviolet (UV) light illumination on the corrosion behavior, surface state, and activities of electro-deposited micro-TiO2/Ni and nano-TiO2/Ni composite foils in 3.5% NaCl solution were investigated by means of polarization measurement, electrochemical impedance spectra (EIS), electron work function mapping (EWF) and XPS spectra analysis using an electrochemical system, the atom force microscopy (AFM) and X-ray photoelectric spectroscopy (XPS), respectively. The UV light illumination resulted in a considerable decrease in corrosion resistance of the nano-TiO2/Ni composite foil but showed much less effect on the micro-TiO2/Ni composite foil. Surface state analysis demonstrated that the UV illumination stimulated the nano-TiO2 semiconductor with elevated conductivity in favor of passing corrosion current. The UV illumination increased the fraction of Ni2O3 component in formed oxide film on the nano-TiO2/Ni foil, which is porous, loose, brittle and less protective, compared to the naturally formed NiO film on Ni. The changes in surface state were responsible for variations in the corrosion behavior of micro-TiO2/Ni and nano-TiO2/Ni composite foils caused by the UV light illumination.