We propose a double-channel narrowband filter based on anomalous large Goos-Hänchen shift reflected from a symmetrical metal-cladding optical waveguide. We demonstrate that two filtering peaks are 859.604nm and 859.688nm respectively. The 3 dB bandwidth is found to be 0.036 nm with an extinction ratio of 15.3dB at a light wavelength of 859.60nm. The filtering peaks can be tuned by choosing an appropriate incident angle and a aperture position.