Abstract: A new type of patch double band-pass filter based on circular substrate integrated waveguide is designed. By loading a circular metal patch, the circular SIW (circular substrate integrate waveguide, CSIW) cavity changes into the composite multilayer circular patch SIW filter. Compared to dual mode CSIW filter, composite multilayer circular patch SIW resonator not only reduces the resonant eigen mode frequency of its main mode, but also adds new modes to form a dual band. To prove its effectiveness, a simulation model is built in HFSS (high frequency structure simulator). Then through parameter optimization, the dual-band composite multilayer circular patch SIW filter is obtained. The results show that the dual-band frequency of the filter is from 1.88 GHz to 2.08 GHz and from 3.35 GHz to 3.60 GHz, and that the upper and lower sidebands of the two passbands have Transmission zeros, which shows good selectivity.