TiO_2films were deposited employing electron beam evaporation te chnique on fused silica and Si substrates and silver nanoparticles with different thicknesses were deposi ted on TiO_2films surface by thermal evaporation technique.The effect of Ag thickness on the structural,morpholog ical,optical and photocatalytic properties of the nanocomposite thin films was investigated,and these properties were obtained by UV-Vis spectrophotometer,X-ray diffraction (XRD),scanning electronmicroscopy (SEM),respectively.The composition and content of elements were determined by energy dispersive spectrometer.The photocatalytic performanc es of the as-synthesized Ag- TiO_2were evaluated in terms of their photodegradation rate of methyl orange ( MO) in an aqueous solution under light.The results show that the Ag nanoparticles are well dispersed on porous Ti O_2surface.The as-prepared Ag- decorated porous TiO_2films exhibits excellent photocatalytic properties.The r esults indicate that the as- deposited Ag-TiO_2thin films are amorphous.It indicates that photocatalytic activity of the samples is enhanced with the thickness of Ag increased until reach to 3.7nm.The Ag-TiO 2films show an enhanced photocatalytic activity compared with pure TiO_2fil ms.