Defective TiO2 attracted increasing attention due to its high photocatalytic activities. Herein, we report a facile and efficient method to fabricate gray defective TiO2 by vacuum annealing raw TiO2 materials with copper powders. The treated TiO2 nanoparticles exhibit significantly enhanced visible-light-photocatalytic performance with photo-degradation rate increased to 400% as that of pristine commercial P25 under visible light. The performance enhancements can be attributed to the disordered structure, optimized optical and electronic properties of defective TiO2. In addition, this facile Cu reduction method provides an effective way to generate defective sites in other metal oxides for various potential applications.