A series of FexAg1-x(x=18, 45, 81) samples were prepared by ion beam sputtering and post-annealed in vacuum at different temperatures for one hour. X-ray diffraction, optical and magneto-optical measurement were performed and the structure, optical and magneto-optical Kerr effect properties for different annealing temperatures have been studied. Results show that the magneto-optical Kerr effects are closely related to the particle size.