Diameters of titania nanotubes could be controlled through changing the oxidation voltages and anodization time. By anodization of one time, the nanotubes with the diameters of 50 nm and 100 nm were fabricated, even of 120 nm for the biggest diameter. By the two-step anodization, however, the diameter of the nanotubes was up to 280 nm, above the limit by one time anodization. It is demonstrated that the increase of voltage in a limited range could increase the diameter of the titana nanotubes, and the diameter of the nanotubes can hardly be expanded beyond 120 nm. In the two-step anodization, the diameter of the nanotubes could be enlarged to a larger range, in which the application of the nanotubes could also be widened.