Based on a sampled-Bragg-grating, a novel approach to obtain high channel-count comb filter is designed for wavelength-division-multiplexing(WDM) system. There is a non-continuous linear chirped structure like a ladder in grating. And refractive index modulation amplitude agrees with Hamming distribution. A 26-channel comb filter with channel spacing of 50 GHz is fabricated. It is able to obtain multiple equalized passbands with flat-top steep-edge and high transmittance, which can be used as optical add/drop multiplexer in WDM system.