A new kind of SnO2 nanotubes loaded with Ag2O nanoparticles can be synthesized by using Ag@C coaxial nanocables as sacrificial templates. The composition of silver in SnO2 nanotubes can be controlled by tuning the compositions of metallic Ag in Ag@C sacrificial templates, and the morphology of tubular structures can be changed by use of nanocables with different thicknesses of carbonaceous layer. This simple strategy is expected to be extended for the fabrication of similar metal-oxide doped nanotubes using different nanocable templates. In contrast to SnO2@Ag@C nanocables as well as to other types of SnO2 reported previously, the Ag2O-doped SnO2 nanotubes exhibit excellent gas sensing behaviors. The dynamic transients of the sensors demonstrated both their ultra-fast response (1-2 s) and ultra-fast recovery (2-4 s) towards ethanol, and response (1-4 s) and recovery (4-5 s) towards butanone. The combination of SnO2 tubular structure and catalytic activity of Ag2O dopants gives a very attractive sensing behavior for applications as real-time monitoring gas sensors with ultra-fast responding and recovering speed.