We report the fabrication of nanoparticle gold thin films by DC magnetron sputtering and characterization of their nonlinear optical properties. Nonlinear optical response was investigated by moiré deflectometery technique using 5mW He- Ne laser (632.8 nm) illumination. All prepared films were characterized by XRD and UV-VIS-NIR spectrophotometry. The measured thermal Nonlinear refractive index (n2=-2.2×10-5 cm2 W-1) makes it promising for applications in all-optical switching devices and optical data storage systems.© (2010) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.