A photoactivated ZnO nanomesh with precisely controlled dimensions and geometries is fabricated by using nanosphere lithography process. The nanomesh structures effectively increase the surface-to-volume ratio to improve the sensing response under the same testing gas. And the periodical nanostructures also increase the effective light path and lead to more efficient light activation for gas sensing. With the increase of the photoinduced oxygen ions by UV illumination, a distinguished sensing response is observed at room temperature. In the optimized case, the sensing response (△R/R0) of the ZnO nanomesh at the butanol concentration of 500 ppm is 97.5%, which is 4.54 times higher than the unpatterned one.