The annealed proton-exchanged(APE)process has emerged as an important technique for the fabrication of low-loss optical waveguides in LiNbO₃. However,the propagation characteristics of this kind of optical waveguides have not been effectively investigated. The propagation characteristics of a silicon-clad x-cut APE channel optical waaveguide as a function of wavelength are investigated by the semi-vectorial beam propagation method. Results for several different waveguide parameters are shown. The results obtained show that attenuation of the propagating mode in this waveguides is highly dependent on wavelength. Moreover,this attenuation characteristic can be controlled by waveguide parameters such as the surface refractive index increment,the thickness of silicon-cladding and the thickness and the refractive index of the buffer layer. As a result,the silicon-clad proton-exchanged optical waveguides can be used as optical frequency filters.