The reason of deactivation of titania whiskers used for deep purification of drinking water and the corresponding regeneration methods were presented. AFM, XRD and ICP were carried out to characterize the titanium dioxide. The experimental results suggest that the main reason of deactivation of titania whiskers is the deposition of calcium carbonate on the catalyst surface. The surface of titania whiskers is covered by the insoluble carbonates generated from carbon dioxide produced during the degradation of organics and metal ions such as calcium in the tap water, and the activity of the titania whiskers decreases gradually till deactivation. After washing by 1 mol/L hydrochloric acid for four hours, the photocatalytic activity of the titania whiskers can achieve 95 percent of that before deactivation. The photocatalytic activity of the titania whiskers which regenerated for many times keeps steady.