In this study, gold-titania catalyst was prepared by photo-deposition method for oxidizing carbon monoxide (CO) to carbon dioxide (CO2). Characterization and activity tests were conducted to investigate the effects of a number of control factors on CO oxidation efficiency, including the precursor pH value, the illumination mode and condition, as well as the reaction temperature. Among these, the precursor pH value was the most profound factor, followed by its interaction effect with the illumination duration. Using controlled periodic illumination mode for photo-deposition resulted in approximately 3-6% performance enhancement compared to using continuous illumination mode due to the formation of smaller gold particle sizes. Regardless the illumination modes, CO oxidation efficiency increased with the reaction temperature up to about 60 degrees C; further increase had not guaranteed any improvement. The same trend was observed for the illumination duration factor (where there existed an optimum value). DRIFTS (Diffuse Reflectance for Infrared Fourier Transform Spectroscopy) results showed the limited reaction of chemisorbed CO with lattice oxygen of the titania support and that purging with oxygen failed to repel the reaction intermediates. Based on the design of experiments-analysis of variance analyses, the estimated best photo-deposition parameters were found to be a precursor pH value of 9, under periodic illumination mode with a frequency of 1,000Hz and duty cycle of 0.2, for an illumination duration of 6.2min.