UV and vacuum treatment, as well as annealing, were tried to recover the gas sensing property of WO3 films. Results show that gas sensing films can partially recover one or two coloring and bleaching cycles if kept in vacuum condition. And UV irradiation can well recover several cycles. But heat treatment does not show any obvious effect on the gas sensing recovery. Furthermore, IR and XPS spectra were used to identify the mechanism of this improvement. Results reveal that changes of water content will reduce the desorption energy of hydrogen atom, which will accelerate the bleaching velocity.© (2010) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.