TaON-Ag nanocomposite thin films with Ag nano-particles emerged on TaON surface were prepared by reactive co-sputtering of Ta and Ag in the plasma of O 2 , N 2 , and Ar. The deposition temperature was 300 °C. The Ag contents were 2.4, 5.0, 10.6 at.% respectively. After deposition, some samples were annealed at 800 °C by rapid thermal annealing (RTA). These films were characterized by a variety of techniques including X-ray diffraction, FESEM (field emission scanning electron microscopy), and TEM (transmission electron microscopy). It is found that co-deposition of Ag into the TaON films leads to several beneficial changes on film properties. Particularly, it is found that Ag nano-particles may emerge on the surface of TaON with or without RTA. This could be much meaningful since Ag particles' appearance is closely related to the antibacterial property of TaON-Ag films with or without visible light irradiation. The results show that TaON-Ag films deposited at 300 °C have a clear increase in antibacterial behavior when irradiated with visible light due to the synergistic effects of Ag and photocatalytic behaviors of TaON. After being annealed, the films show even more promising antibacterial behavior. Photodegradation testing of methylene blue also comes to similar conclusions.