Abstract: The design of Classical microwave cavity filter requires large numbers of complicated formulae and numerous curves.A fast and simple design method can avoid these process.Taking pectinate bandpass filter for example,by calculating some typical normalized diameters and spaces between of poles,a fast and simple design curves is obtained in which,X-coordinate is for relative wideband,Y-coordinate is for normalized diameter and space between of pole respectively.By means of ANSOFT-HFSS software,structure simulation for this microwave bandpass filter designed by this ways can be achieved.Finally,A satisfactory structure size is obtained,which meets the specifications and the validity is proved by experimental result.