Binary glasses of Ge25Se75 are prepared by melt quench technique. Two layers of thin film have been done by the conventional thermal evaporation technique on glass substrate. Ge25Se75 with 340±5 nm thickness is prepared as first layer, then thin silver layer is evaporated on top of the Ge25Se75 film. The Ge25Se75 with Ag on top of the film were annealed at different time of 30, 60, 90, and 180 and 210 min at temperature of 573 K. Subsequently, we have analyzed these films using scanning electron microscopy (SEM) and X-ray diffraction (XRD) to confirm the successful diffusion of Ag on Ge25Se75 films. XRD measurements show that as prepared Ag/Ge25Se75 have amorphous natures. Optical transmission and reflection spectra of the studied thin films are measured in the wavelength range of 200–2500 nm at room temperature. The optical properties of the new films were studied before and after annealing at different annealing times due to gradually thermal diffusing of Silver on Ge25Se75. The absorption coefficient (α) as an optical constant is determined as a function of annealing times. Moreover, the values of the third-order nonlinear optical susceptibility increased with an increase of annealing temperatures due to gradually thermal diffusing of Silver. The gradual thermal diffussion of Ag on amorphous GeSe thin film causes a change in the nonlinear refractive index and third order type nonlinear optical susceptibility. The results indicate that Ag/Ge25Se75 has great potential for various applications including optical sensors and optoelectronics.