An excellent visible-light-responsive (from 400 to 550 nm) TiO 2− x N x photocatalyst was prepared by a simple wet method. Hydrazine was used as a new nitrogen resource in this paper. Self-made amorphous titanium dioxide precursor powders were dipped into hydrazine hydrate, and calcined at low temperature (110 °C) in the air. The TiO 2− x N x was successfully synthesized, following by spontaneous combustion. The photocatalyst was characterized by X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), transmission electron microscope (TEM), UV–Vis diffuse reflectance spectrometer (DRS), and X-ray photoelectron spectroscopy (XPS). Analysis of XPS indicated that N atoms were incorporated into the lattice of the titania crystal during the combustion of hydrazine on the surface of TiO 2. Ethylene was selected as a target pollutant under visible-light excitation to evaluate the activity of this photocatalyst. The newly prepared TiO 2− x N x photocatalyst with strong photocatalytic activity and high photochemical stability under visible-light irradiation was firstly demonstrated in the experiment.