The nanoporous TiO2 film electrodes have been prepared by a sol-gel deposition process.The photostability of the electrodes in basic solutions has been studied. The results show that the photostability of the electrodes decreases rapidly in strong basic solutions with or without methanol. The reaction of holes to O2-ad produces active O-ad atoms and the products O-ad atoms oxidize Ti3+ to Ti4+ on TiO2 film surface and subsurface. This results in the TiO2 film electrodes unstable in basic solutions both without methanol and with too low concentration.