The Goos-Hnchen effect,which is enhanced by the resonance of the guided mode in a symmetrical metal-cladding waveguide with submillimeter scale,is used to detect the slight variation of wavelength.The symmetrical metal-cladding waveguide consists of a guiding layer and two metal-cladding layers.When the laser beam incidents on the surface of the coupling prism with a small incident angle,the ultrahigh-order mode will be excited under the phase-matching condition,which exhibits a strong dispersion ability of the wavelength.Theoretical analysis indicates that the GH lateral shift is closely related to the intrinsic and radiative dampings of the waveguide.As the two dampings of SMCW approach to the best matching condition,the GH shift will exhibit a great enhancement and the lateral GH shift may reach several hundreds of microns.Since the detecting signal is proportional to the displacement of the light beam,the measurement will not be affected by the fluctuation of the light intensity.A wavelength resolution of 0.2 pm near the wavelength of 859 nm is demonstrated in experiment.