Abstract: A kind of rigorous design method for microwave and millimeter-wave filters is (presented).The element values for distributed low-pass prototype filter are transformed into(general) K-inverters.Coupling junctions are computed by Mode-Matching Technique(MMT) or Coupled(Integral) Equations Technique(CIET) to achieved the exact S parameters and K-inverters(corresponding).All dimensions of coupling junctions and the length of resonators are obtained by(using) interpolation,and the filter is simulated by MMT program,HFSS or CST software,the(simulation) result agree well with the predicted values,and optimization is not needed during the(design) progress.A 26GHz rectangular waveguide band-pass filter is designed,both the simulation result by MMT,HFSS and CST and measured date keep good agreement with prototype values.This show that the design method is valid.