In this work, an effective photocatalytic inactivation of Escherichia coli K-12 was investigated using a series of synthesized Ag/AgX-CNTs (X = Cl, Br, I) composites as photocatalysts under visible light (VL) (? = 400 nm) irradiation. The results showed that the visible-light-driven (VLD) Ag/AgBr-CNTs could completely photocatalytically inactivate 1.5 נ107 cfu mL-1 of E. coli within 40 min, which was superior to Ag/AgCl-CNTs and Ag/AgI-CNTs. Moreover, photocatalytic bactericidal mechanism of the Ag/AgX-CNTs was investigated by using various scavengers to remove the respective reactive species and at different wavelengths of VL. It was found that photocatalytic inactivation of E. coli was much more efficient under VL with 435 nm wavelength and the photogenerated holes played an important role in this photocatalytic inactivation system. In addition, the stability and deactivation mechanism of Ag/AgX-CNTs photocatalysts during photocatalytic bacterial inactivation were also studied, and the results showed that the organic debris of decomposed bacteria may be absorbed on the active sites of the photocatalysts leading to the decrease of the photocatalytic activity.