A novel broadband substrate integrated waveguide bandpass filter was presented based on the highpass characteristics of substrate integrated waveguide(SIW) and the bandstop performance of butterfly radial slot photonic band gap(PBG) structure. In order to verify this idea，a wideband bandpass filter with 4.65 GHz center frequency and 40% fractional bandwidth was designed. The electromagnetic simulation results show good passband characteristics from 3.71 to 5.6 GHz, while the maximun insertion loss is about 0.40dB. An experimental filter prototype was fabricated with standard PCB process and measured by the vector network analyzer. The measured results show that, for the filter prototype, the passband is from 3.78 GHz to 5.76GHz, the fractional bandwidth is about 41%, the minimal insertion loss is about 0.72 dB and the maximun insertion loss is 1.65.dB The measured results are in good agreement with the simulated results.