Novel one-step synthesis route for S-doped TiO2 photocatalysts by flame spray pyrolysis (FSP) for visible light photocatalysis was developed. We observed improved visible light absorption and reduction of the band gap energies to 2.78 eV. Addition of sulfur in the TiO2 promoted the anatase to rutile transformation in the prepared catalysts. The S oxidation states along with optical properties of the catalyst were studied using X-ray photoelectron spectroscopy (XPS) and UV-Vis spectroscopy. The oxidation state of the S atoms incorporated into the TiO2 is determined to be mainly S4+ and S6+ in the XPS spectra. Among all the synthesized catalysts, catalyst with 2M sulfuric acid in precursor illustrated an impressive performance for the visible light induced photocatalysis along with higher S6+/S4+ of 5.61. The S+6 presence has important role in enhancing the visible light photocatalytic activity. The photocatalytic activity of the sulfur-doped TiO2 was evaluated through the degradation of acetaldehyde under visible light irradiation. Our results show that we developed a new synthesis method to achieve stable and highly efficient solar light-driven S-modified TiO2 photocatalysts for water purification.