The success of communication systems is directly related to the availability of an effective technology in terms of cost and suitable for mass-production of components. Substrate-Integrated Waveguide (SIW) technology represents an promising candidate for the development of circuits and components operating in the microwave and millimeter-wave region. SIW structures permit the implementation of waveguide components in planar form, along with active devices and antennas. Due to the unique properties of the SIW structure, using this structure for design of microwave and millimeter wave components has increased dramatically over the last decade. Actually, the ease of fabrication, low-profile, low-weight and low-cost are the advantages of SIW structures. Among the variant of SIW components, It is paid more attention to SIW filters due to their higher quality factor compared to microstrip and co-planar filters.Therefore, the object of this thesis is to design and fabrication an SIW broadband filter with the novel structure. At the beginning by cuttings on the patch of equilateral triangle cavity, The resonators with smaller dimensions are achieved. then, by proper arrangement of the resonators next to the each other, a filter with small dimensions and high bandwidth is designed. In the next step, to improve its out of band response, the band-gap property of the Defected Microstrip Strucure (DMS) is used. Finally, The proposed filter is fabricated and tested. Observed that, the measurement results are in good agreement with simulation results. Key word: Substrate Integrated Waveguide, Broadband Filter, Cavity, Resonator