Ag nanoparticles (NPs) thin films with various thicknesses were prepared by thermal evaporation method. Atomic force microscopy (AFM) and UV-Vis spectrophotometer were used to study the surface morphology, growth nature and optical properties of the films. The results indicate that the growth rates of Ag particles in lateral and vertical direction are variable, and the dominant growth rate of Ag particles in lateral direction will convert into dominant growth rate in vertical direction as films grow thicker. The mean value and distribution of Ag NPs height related with the location and width of SPR (surface plasmonresonance) peak. Higher mean height shifts SPR peak to longer wavelengths, and smaller deviation results in narrower width of SPR peaks.