Thin TiO2 films in-situ grown on titanium alloy substrate were prepared in 0.05 mol/L H2SO4 electrolyte using the micro plasma oxidation method. The photocatalytic properties of the prepared thin TiO2 films were investigated using Rhodamine B solution as a target pollutant. In order to improve the photocatalytic properties of the obtained TiO2 films, different contents of Nb(NO3)3 were added into the H2SO4 electrolyte and the Nb-doped TiO2 films in situ growth were obtained. The influences of the doping ions on the surface morphologies, the crystal phase compositions and microstructures of the TiO2 films were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The results show that doping of Nb ions can refine the mesoporous TiO2 grain and increase the specific surface area. But doping of Nb ions has little influence on the crystal phase composition and the lattice parameters. Otherwise, doping of Nb ions can improve the photocatalytic activity of TiO2 thin films, when the Nb(NO3)3 is 1.2 g/L, the degradation rate of Rhodamine B solution in 90 min reaches 85%, showing the strongest light degradation ability